Loop 1
Heated layout share: 297.5 ft
Leader allowance: 0 ft
Total planned length: 297.5 ft
Hydronic Heating Radiant Loop Calculator
Your Floor
Only area intended to receive tubing, not total building area. No automatic deductions for cabinets or unusable floor.
Descriptive only. Size changes do not alter geometric coverage or select a loop-length target.
Enter a preset or custom spacing; measured between neighboring tube centerlines.
Preset equivalents preserve physical spacing. No preset is a heating-performance recommendation.
Loop Planning
Example planning limit — verify for your system. Default 300 ft / 91.44 m is an example, not a universal limit. Leave blank for tubing quantity without a loop recommendation.
Visible, editable allowance for installation planning: 0–100%. Default 5% is an example, not a routing calculation.
Loop-length limits vary by tubing, flow target, pressure drop, manifold/circulator design, and manufacturer guidance. Use a project-appropriate maximum loop length.
Advanced: leaders and purchase rounding
Combined supply/return leader allowance from manifold to heated area, added once per loop. Enter the combined total; do not double it again.
Positive custom increment; quantity rounding only, not a claim about available coils.
Enter any supported custom increment directly.
Area ÷ spacing approximates evenly spaced coverage. It does not model room shape, edges, turns, obstacles, cabinets, perimeter zones, manifold position, supply/return routing or unusable area. Enter only the heated area intended to receive tubing.
Software bounds in normalized SI: area 0.000000001–1,000,000,000 m²; spacing 0.000000001–1,000,000 m; positive target/increment up to 1 trillion m; leaders 0–1 trillion m; derived quantities up to 1 trillion m. Loop plans support up to 1,000 loops. These are software limits, not design criteria.
Recommended Layout
RADIANT LOOP PLAN
3 loops
Minimum count meeting your selected loop-length target under the geometric model.
- Estimated tubing required
- 892.5 ft
- Average loop length
- 297.5 ft
- Tube spacing
- 12 in
- Manifold circuits needed
- 3
- Selected loop-length target
- 300 ft / loop
- Suggested purchase quantity
- 900 ft
Purchase rounded upward in 100 ft increments. This does not change loop count, average or target status, and does not represent coil availability.
Why This Many Loops?
892.5 ft of heated layout with allowance. 2 loops average 446.25 ft, exceeding the selected 300 ft target. 3 loops average 297.5 ft, within the selected target. This is the smallest integer count meeting that target; decisions use unrounded values.
Hydronic note: This calculator estimates tubing quantity and loop layout geometry. It does not determine heat loss, heat output, required flow, pressure drop, pump size, water temperature, control strategy, or code compliance.
Actual heating performance depends on the complete floor assembly, coverings, insulation, water temperatures, flow, and room heat loss.
Planned average loop allocation
BALANCED BY CALCULATION: equal geometric allocations, with a floating-point residual assigned to the last loop. This does not establish hydraulic balance or actual installed routing.
Loop 2
Heated layout share: 297.5 ft
Leader allowance: 0 ft
Total planned length: 297.5 ft
Loop 3
Heated layout share: 297.5 ft
Leader allowance: 0 ft
Total planned length: 297.5 ft
Alternate loop counts
Each option recomputes its own leader total. Target decisions use raw values, even when rounded averages look equal.
2 loops
Total tubing: 892.5 ft
Leaders: 0 ft
Average: 446.25 ft
EXCEEDS SELECTED TARGET
3 loops — selected
Total tubing: 892.5 ft
Leaders: 0 ft
Average: 297.5 ft
WITHIN SELECTED LOOP-LENGTH TARGET
4 loops
Total tubing: 892.5 ft
Leaders: 0 ft
Average: 223.13 ft
WITHIN SELECTED LOOP-LENGTH TARGET
What if I change spacing?
Same area, installation allowance, target and leader allowance. Fewer loops are not inherently better; spacing also affects heating design, which this calculator does not evaluate.
6 in
Estimated tubing: 1,785 ft
Minimum loops: 6
Average: 297.5 ft
8 in
Estimated tubing: 1,338.75 ft
Minimum loops: 5
Average: 267.75 ft
9 in
Estimated tubing: 1,190 ft
Minimum loops: 4
Average: 297.5 ft
12 in
Estimated tubing: 892.5 ft
Minimum loops: 3
Average: 297.5 ft
Material planning summary
1/2 in nominal tubing · estimated 892.5 ft · 3 manifold circuits · spacing 12 in · purchase quantity 900 ft.
No fittings, clips, fasteners, plates, costs or specific manifold products are inferred.
Layout schematic
Show calculation
Base tubing length = heatedArea / spacing (m² / m = m); in US units, baseLengthFt = areaFt² × 12 / spacingIn. Layout with allowance = base × (1 + allowancePct / 100). Find the smallest integer N with layoutWithAllowance / N + leaderPerLoop ≤ targetMaxLoopLength. Total tubing = layoutWithAllowance + N × leaderPerLoop. With zero leaders, N = ceil(layoutWithAllowance / target).
Base tubing: 850 ft; allowance 5%; layout with allowance 892.5 ft; leader total 0 ft; estimated total 892.5 ft.
Layout and design sources
- Uponor: radiant systems and on-center spacing terminology (opens in a new tab)
- Uponor: floor properties, pipe spacing and floor structure (opens in a new tab)
- Uponor: hydraulic calculations, loops and feed pipes (opens in a new tab)
- NIST Guide to the SI: exact length conversion factors (opens in a new tab)
Radiant loop plan
Hydronic Heating Radiant Loop Calculator Heated area: 850 ft² Tube size: 1/2 in (descriptive only) Center-to-center spacing: 12 in Installation allowance: 5% (explicit, editable) Base tubing length = heatedArea / spacing (m² / m = m); in US units, baseLengthFt = areaFt² × 12 / spacingIn. Layout with allowance = base × (1 + allowancePct / 100). Find the smallest integer N with layoutWithAllowance / N + leaderPerLoop ≤ targetMaxLoopLength. Total tubing = layoutWithAllowance + N × leaderPerLoop. With zero leaders, N = ceil(layoutWithAllowance / target). Base tubing: 850 ft Layout with allowance: 892.5 ft Leader per loop: 0 ft Selected maximum loop length: 300 ft (project-specific; default 300 ft is an example planning limit, verify for your system) Estimated tubing: 892.5 ft Loops: 3 Average loop length: 297.5 ft Leader total: 0 ft Manifold circuits needed: 3 WITHIN SELECTED LOOP-LENGTH TARGET 892.5 ft of heated layout with allowance. 2 loops average 446.25 ft, exceeding the selected 300 ft target. 3 loops average 297.5 ft, within the selected target. This is the smallest integer count meeting that target; decisions use unrounded values. Suggested purchase quantity: 900 ft; rounding increment 100 ft. Quantity only, not available coil products. Planned average loop allocation — BALANCED BY CALCULATION Loop 1: heated share 297.5 ft; leader 0 ft; total 297.5 ft Loop 2: heated share 297.5 ft; leader 0 ft; total 297.5 ft Loop 3: heated share 297.5 ft; leader 0 ft; total 297.5 ft Alternate loop counts 2 loops: total 892.5 ft, average 446.25 ft, leaders 0 ft; EXCEEDS SELECTED TARGET 3 loops: total 892.5 ft, average 297.5 ft, leaders 0 ft; WITHIN SELECTED LOOP-LENGTH TARGET 4 loops: total 892.5 ft, average 223.13 ft, leaders 0 ft; WITHIN SELECTED LOOP-LENGTH TARGET What if I change spacing? 6 in: 1,785 ft, 6 loops, average 297.5 ft 8 in: 1,338.75 ft, 5 loops, average 267.75 ft 9 in: 1,190 ft, 4 loops, average 297.5 ft 12 in: 892.5 ft, 3 loops, average 297.5 ft BALANCED BY CALCULATION describes equal geometric allocations only. It does not establish hydraulic balance. Fewer loops are not inherently better. Area ÷ spacing approximates evenly spaced coverage. It does not model room shape, edges, turns, obstacles, cabinets, perimeter zones, manifold position, supply/return routing or unusable area. Enter only the heated area intended to receive tubing. Schematic only — not a routing plan. Hydronic note: This calculator estimates tubing quantity and loop layout geometry. It does not determine heat loss, heat output, required flow, pressure drop, pump size, water temperature, control strategy, or code compliance. Loop-length limits vary by tubing, flow target, pressure drop, manifold/circulator design, and manufacturer guidance. Use a project-appropriate maximum loop length. Actual heating performance depends on the complete floor assembly, coverings, insulation, water temperatures, flow, and room heat loss. Uponor: radiant systems and on-center spacing terminology: https://www.uponor.com/en-ca/solutions/radiant Uponor: floor properties, pipe spacing and floor structure: https://ufhrevit.uponor.com/Manual/10.%20Floor%20Properties/Floor%20Properties.html Uponor: hydraulic calculations, loops and feed pipes: https://ufhrevit.uponor.com/Manual/22.%20Hydraulic%20Calculations/Hydraulic%20Calculations.html NIST Guide to the SI: exact length conversion factors: https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors
How to use
Estimate radiant-floor tubing from heated area and spacing. Plan loops, leaders, manifold circuits and purchase rounding against your selected loop-length target.
Enter the heated area and center-to-center spacing in Your Floor. Tubing size is descriptive. In Loop Planning, enter a design/manufacturer loop-length target and visible installation allowance. Advanced contains combined supply/return leaders per loop and optional purchase rounding. Unit changes preserve physical measurements; preset buttons are conveniences. Copy Radiant Loop Plan includes inputs, formulas, allocation, comparison and limitations. Print / Save PDF includes the schematic and plan using your browser. Reset restores the labeled example: 850 ft², 12 in, 1/2 in tube, 5%, 300 ft target, zero leaders, 100 ft rounding and US units.
How radiant tubing length is estimated
Base tubing length = heatedArea / spacing (m² / m = m); in US units, baseLengthFt = areaFt² × 12 / spacingIn. Layout with allowance = base × (1 + allowancePct / 100). Find the smallest integer N with layoutWithAllowance / N + leaderPerLoop ≤ targetMaxLoopLength. Total tubing = layoutWithAllowance + N × leaderPerLoop. With zero leaders, N = ceil(layoutWithAllowance / target).
The coverage approximation comes from parallel tube runs covering strips of floor: area ≈ total run length × center-to-center spacing, hence length ≈ area / spacing. This dimensional derivation is the calculator’s planning model, not a manufacturer routing algorithm. It applies the allowance once, before leaders. The default yields base 850 ft and layout with allowance 892.5 ft.
Area ÷ spacing approximates evenly spaced coverage. It does not model room shape, edges, turns, obstacles, cabinets, perimeter zones, manifold position, supply/return routing or unusable area. Enter only the heated area intended to receive tubing.
Heated floor area
Heated floor area means the area actually intended to receive radiant tubing. Do not enter a whole-building figure if cabinets, unheated rooms or other exclusions reduce the tubing area. This calculator makes no automatic subtraction for unusable floor, edges or obstacles. Measure or obtain the heated-zone area separately. Supported units are ft² and m²; 850 ft² equals 78.967584 m².
Tube spacing
Spacing is measured center to center between adjacent tube runs, not clear distance between tube walls. Choose 6, 8, 9 or 12 in equivalents or enter a positive custom value in inches, millimeters or centimeters. Smaller spacing increases geometric tubing quantity for the same heated area. Spacing choice still needs a separate thermal design.
Uponor’s floor properties documentation (opens in a new tab) treats pipe spacing and floor structure as separate design inputs. Its radiant systems page (opens in a new tab) uses on-center spacing terminology for Fast Trak. Here preset equivalents are 152.4, 203.2, 228.6 and 304.8 mm.
For a measurement check, convert fractional-inch tubing spacing before entering a custom center-to-center spacing. Check the selected units; conversion does not establish suitable thermal spacing.
Tubing size
Choose nominal 3/8, 1/2, 5/8 or 3/4 in tubing for the material summary. Tubing size does not change area/spacing geometry or the entered target in this calculator. Hydraulic design and product selection remain separate. These nominal inch choices are descriptions, not metric product-size conversions or outside-diameter measurements.
Installation allowance
layoutWithAllowance = baseTubingLength × (1 + allowancePct / 100). The default 5% is visible and editable from 0% to 100%. No hidden 5%, 10% or 15% factor is added. Select an allowance for your own installation; it does not automatically measure turns, waste or room routing. Leader allowance is added separately once per planned loop, avoiding a silent doubled supply/return allowance.
Loop count
With zero leaders, minimumLoopCount = ceil(layoutWithAllowance / targetMaxLoopLength). With leaders, total tubing depends on count: total = layoutWithAllowance + N × leaderPerLoop. The engine iterates N from 1 to the software maximum of 1,000, seeking the smallest count where layoutWithAllowance / N + leaderPerLoop ≤ target. The default gives ceil(892.5 / 300) = 3 loops and 297.5 ft average.
Raw values determine the comparison. Only a machine-precision allowance for floating-point conversion noise is used, not a design margin or rounded displayed average.
Loop length target
Loop-length limits vary by tubing, flow target, pressure drop, manifold/circulator design, and manufacturer guidance. Use a project-appropriate maximum loop length.
Example planning limit — verify for your system. The default 300 ft / 91.44 m is explicitly an example, not a recommended maximum for all tubing or projects. Leave the target blank to estimate heated-layout tubing without a loop recommendation, average, leader total or manifold count. An invalid target clears results. No manufacturer numeric maximum is generalized on this page.
Leader/manifold allowance
The optional leader input is the combined manifold-to-heated-area supply/return allowance per loop. leaderTotal = N × leaderPerLoop; estimated total = heated layout with allowance + leaderTotal. Adding leaders can require more loops, which adds more leaders; all candidate counts are recomputed coherently. Leaders must be shorter than the selected target so positive heated-loop length remains. With a blank target, the estimate excludes unresolved leaders.
Uponor’s hydraulic calculations documentation (opens in a new tab) distinguishes loop length within the floor, feed-pipe length and their combined total. Our leaders are a user allowance rather than measured routing.
Balancing loop lengths
Planned average loop allocation uses equal geometric totals, with any floating-point residual assigned deterministically to the last loop. Raw allocated totals sum to the raw total. BALANCED BY CALCULATION describes these equal planning lengths only. It does not establish hydraulic balance, actual installed loop lengths or flow settings. Actual routing may differ and needs its own design.
Manifold circuits
Manifold circuits needed = planned loop count. One circuit represents the corresponding supply/return connections for a loop, not a total of all individual connection fittings. This is a minimum circuit count for the plan; no brand, manifold model, valve size or commercial port configuration is selected.
Comparing spacing options
The What if I change spacing? cards rerun the same geometry engine at 6, 8, 9 and 12 in equivalents using the current area, allowance, target and leaders. They show total tubing, minimum loop count and average. No target means quantity only. N−1, N and N+1 comparison cards independently recalculate leader totals and compare raw average lengths with the entered target. Fewer loops are not inherently better.
Heat-output limitations
Actual heating performance depends on the complete floor assembly, coverings, insulation, water temperatures, flow, and room heat loss.
No BTU/h, watts, heat load, heating adequacy or capacity rating is derived from area, spacing or tube size. Floor covering, water temperature and room temperature inputs are omitted because this geometry model cannot use them to evaluate performance. Uponor’s floor-properties reference includes covering resistance, insulation and other floor layers, illustrating information needed beyond this estimate.
Hydraulic limitations
Hydronic note: This calculator estimates tubing quantity and loop layout geometry. It does not determine heat loss, heat output, required flow, pressure drop, pump size, water temperature, control strategy, or code compliance.
Equal loop length does not establish equal pressure drop or flow. This tool gives no GPM recommendation, head loss, feet of head, pump selection, boiler sizing, flow setting or control strategy. The linked Uponor hydraulic documentation separately considers flow, temperatures and pressure drop. A project-specific loop target must come from your design/manufacturer process.
To estimate circuit water capacity separately, calculate volume in tubing with a known inside diameter and a verified length. Nominal tubing size is not necessarily its inside diameter, and volume alone does not establish pressure drop, required flow or pump suitability.
Worked examples
1. 850 ft², 12 in spacing, 5%, 300 ft example target
Base 850 ft; allowance 5%; heated layout with allowance 892.5 ft; loops 3; heated share per loop 297.5 ft; leader per loop 0 ft; leaders total 0 ft; total tubing 892.5 ft; average 297.5 ft; target 300 ft; manifold circuits 3.
2. Same floor with 8 in spacing
Base 1,275 ft; allowance 5%; heated layout with allowance 1,338.75 ft; loops 5; heated share per loop 267.75 ft; leader per loop 0 ft; leaders total 0 ft; total tubing 1,338.75 ft; average 267.75 ft; target 300 ft; manifold circuits 5.
3. 20 ft combined leaders per loop cause an extra loop
Base 850 ft; allowance 5%; heated layout with allowance 892.5 ft; loops 4; heated share per loop 223.13 ft; leader per loop 20 ft; leaders total 80 ft; total tubing 972.5 ft; average 243.13 ft; target 300 ft; manifold circuits 4.
4. 80 m², 300 mm spacing, 5%, 90 m example target
Base 266.67 m; allowance 5%; heated layout with allowance 280 m; loops 4; heated share per loop 70 m; leader per loop 0 m; leaders total 0 m; total tubing 280 m; average 70 m; target 90 m; manifold circuits 4.
5. Default N−1 / N / N+1 comparison
2 loops: tubing 892.5 ft, leaders 0 ft, average 446.25 ft — EXCEEDS SELECTED TARGET.
3 loops: tubing 892.5 ft, leaders 0 ft, average 297.5 ft — WITHIN SELECTED LOOP-LENGTH TARGET.
4 loops: tubing 892.5 ft, leaders 0 ft, average 223.13 ft — WITHIN SELECTED LOOP-LENGTH TARGET.
Assumptions and limitations
Area ÷ spacing approximates evenly spaced coverage. It does not model room shape, edges, turns, obstacles, cabinets, perimeter zones, manifold position, supply/return routing or unusable area. Enter only the heated area intended to receive tubing.
The target, allowance and leader values are entered assumptions, not installation standards. Purchase quantity uses ceil(total / increment) × increment after loop calculations; its presets of 50 and 100 ft equivalents are rounding increments, not available coil products. Purchase rounding cannot change loops, average or target status. No fasteners, plates, fittings or cost factors are invented.
Internal area, spacing and lengths use SI meters and square meters at full floating-point precision. NIST gives 1 ft = 0.3048 m exactly; thus 1 in = 0.0254 m. US/metric and spacing-unit changes cache unrounded physical values; editing creates a new value. Outputs generally show up to two decimals, percentages one decimal. Input strings are bounded to 64 characters; comma or dot decimals are accepted through the shared NumericInput.
Software bounds: positive area up to 1 billion m², positive spacing up to 1 million m, positive targets/increments and nonnegative leaders up to 1 trillion m; derived lengths up to 1 trillion m; up to 1,000 loops. Positive SI inputs must be at least 0.000000001. Large finite floors are supported within those broad limits; divide larger loop plans into zones. Invalid or nonfinite inputs clear results and disable copy/print. Calculations stay local to the page session, without saved projects, numeric URL persistence or network calculations.
FAQ
How do I estimate radiant-floor PEX tubing length?
Divide heated area by center-to-center spacing in consistent units. For ft² and inches, multiply area by 12 and divide by spacing. Add the editable installation allowance, then any per-loop leaders after choosing a loop count.
How does tube spacing affect total tubing length?
At fixed heated area, base tubing length varies inversely with spacing. Halving spacing doubles the geometric base length. This does not calculate the resulting heat output.
How do I calculate how many radiant loops I need?
Enter your project-specific maximum loop length. The engine checks integer counts upward until layout length divided by count plus the leader allowance per loop fits that target.
What is a reasonable radiant-loop length?
Use the design or manufacturer target appropriate to your system. The default 300 ft is an example planning limit only. This calculator does not recommend a universal maximum.
Why does maximum loop length vary by system?
Tubing, intended flow, pressure drop, manifold and circulator design, and manufacturer guidance affect the project target. A geometry-only calculation cannot establish the permissible length.
Does PEX size change how much tubing covers the floor?
At the same heated area and center-to-center spacing, all four nominal sizes produce the same geometric coverage length here. Size remains relevant to separate system design.
How much extra tubing should I allow for turns and routing?
Enter an explicit installation allowance appropriate to your layout and a separate combined supply/return leader allowance per loop. The editable 5% example is not an automatic measurement of turns.
How many manifold ports do I need?
The plan needs one manifold circuit for each planned loop, typically a corresponding supply-and-return connection pair. This is a circuit count, not a branded manifold selection.
Can this calculator determine radiant-floor heat output?
No. A complete floor assembly, covering resistance, insulation, temperatures, flow and room heat loss are needed for thermal design. No capacity or adequacy rating is produced.
Does this calculator size the pump, boiler, or determine code compliance?
No. It estimates quantities and geometric loop allocations only; pump, boiler, pressure drop, controls and compliance require separate design.
Sources
Sources checked October 4, 2026. Uponor’s documentation supports spacing terminology, floor-assembly context, and the distinction between loops, feed pipes and hydraulic design. The area/spacing approximation and iterative count solver are explained here as this calculator’s own geometry model. NIST supports exact length conversions. These references do not endorse BuzCalculator or make the example target a universal limit.
- Uponor: radiant systems and on-center spacing terminology (opens in a new tab)
- Uponor: floor properties, pipe spacing and floor structure (opens in a new tab)
- Uponor: hydraulic calculations, loops and feed pipes (opens in a new tab)
- NIST Guide to the SI: exact length conversion factors (opens in a new tab)