Changing units converts the entered dimensions.
1–10 whole coats. Primer is excluded.
Converts physical coverage when changed.
Required for paint quantity. Enter your product’s coverage per coat; equivalent to 0.01–1,000 m²/L.
Context only. Surface condition can affect actual coverage; use the product’s preparation and coverage information. No numerical multiplier.
0–100%. No percentage is universally recommended.
Converts entered package volumes.
Label only; no currency conversion or price lookup.
Enter product coverage to calculate paint quantity.
Project painted area: 40.134113 m² · Across 2 coats: 80.268227 m²
Entered product coverage: Not supplied
Selected extra allowance: 0%
Gross wall area: 2 × (3.6576 + 4.572) × 2.4384 = 40.134113 m². Ceiling: 3.6576 × 4.572 = 16.722547 m².
Openings: 0 m², deducted from walls only. Net wall area: 40.134113 − 0 = 40.134113 m².
Net included area: 40.134113 m². Coats contribution: 40.134113 × 2 = 80.268227 m².
Combined painted area: 40.134113 = 40.134113 m². Coated area: 40.134113 × 2 = 80.268227 m².
Displayed arithmetic is rounded to six decimals; calculations retain full numeric precision.
Enter product coverage before calculating packages.
Least unused: minimize purchased volume, then fewer packages, then earlier listed types. Lowest entered price: minimize cost, then unused volume, fewer packages and earlier listed types. Only complete pricing permits the lowest-price comparison. A selected combination’s cost is the sum of count × entered price for its used packages.
Modeled quantities depend on entered measurements, product coverage and coats. Actual coverage can differ. No primer, surface multiplier, tax, labor or delivery is included. Package results compare only the entered options; availability and suitability are not verified.
Rectangular rooms only; avoid overlapping surfaces. All rooms share coverage, coats and extra. Separate products need separate estimates. Surface context: Smooth; no quantity adjustment. Package optimization is limited to 1,000 L, 1,000 packages per type and 200,000 search nodes; no partial optimum is shown.
Estimate paint from room dimensions, coats and your product coverage. Compare entered packages by unused volume and entered price.
Measure each rectangular room’s length, width and wall height in one dimension unit. Select Walls, Ceiling or Walls + Ceiling. The initial 12 × 15 × 8 ft room and two coats are editable examples. Product coverage starts blank: no paint quantity is supplied until you enter that product assumption.
Measure doors, windows or other wall areas you intend to exclude as individual width × height openings. No standard door or window dimensions are assumed. Up to twenty rooms and fifty openings per room are supported. Avoid overlapping rooms or counting the same wall area twice.
Gross wall area = 2 × (length + width) × height. Ceiling area = length × width. Opening area = sum(width × height). Net wall area = gross wall area − opening area. Walls mode includes net walls, Ceiling includes only the ceiling, and Both adds the two. Openings never reduce the ceiling. Opening totals greater than gross wall area are rejected, including in ceiling mode; equality is allowed.
Project painted area is the sum of included room areas. Coated area = project painted area × coats. Choose 1, 2, 3 or a custom whole number from 1–10. Rooms are combined before dividing by coverage or rounding packages, so this is one paint product estimate for the whole project. Different products, coverage rates or coats by room need separate estimates.
Paint before extra = coated area ÷ entered product coverage per coat. Use the coverage information for the product and surface you are working with, in m²/L or ft²/US gallon. A coverage rate for an entire multi-coat system should not be entered as a per-coat rate without checking its meaning.
Smooth, Textured, Porous and Other are context labels only. Surface condition can affect actual coverage; consult the product’s preparation and application information. Selecting a surface never inserts a coverage number or silently adds a multiplier. This tool models the rate you enter, rather than predicting absorption or application losses.
Purchase target = paint before extra × (1 + selected extra percentage / 100). The 0%, 5%, 10% and 15% shortcuts and custom 0–100% field are user assumptions; none is universally recommended. The default is 0%. Paint before extra and purchase target remain visible separately.
Dimension units are feet, inches, meters and centimeters. Changing units converts entered quantities rather than reinterpreting the numbers. Canonical arithmetic uses meters, m² and liters. Exact base definitions: 1 ft = 0.3048 m; 1 in = 0.0254 m; 1 cm = 0.01 m; 1 US gallon = 231 cubic inches = 3.785411784 L. This is not an imperial gallon. Coverage in ft²/US gallon converts to m²/L by multiplying by 0.3048² / 3.785411784. No deliberate internal rounding is used; displays show up to six decimals.
Enter up to six available package sizes, with optional labels and prices. No retail sizes are prefilled. A covering combination must supply at least the combined purchase target. Least-unused modeled combination minimizes purchased volume minus target, then the number of packages. Remaining ties prefer more packages of the earlier listed type at the first differing count.
Lowest entered-price combination independently minimizes sum(count × entered price). It then minimizes unused volume, package count and uses the same input-order tie-break. Both combinations appear if different; if identical, the result identifies that. All package types must have prices for a lowest-price comparison. Zero prices are permitted. With incomplete pricing, a selected least-unused combination still has a cost if every package it uses has a price, but no globally cheapest claim is made.
The deterministic search enumerates whole counts from zero through ceil(target / package volume) for each type. Once a combination covers the target, adding more positive-volume packages cannot improve unused volume or nonnegative cost, so that branch ends. A larger count than this per-type bound is also dominated. All objective comparisons use unrounded numeric values.
Search is capped at a 1,000 L target, 1,000 packages per type and 200,000 visited search nodes. If any bound is exceeded, no partial optimum is reported. The geometry and paint result remain available with an explicit package limitation. This is an optimizer over entered options, not a guarantee of retail availability, product compatibility or practical packaging.
Package cost is count × entered price for each used type, summed without internal currency rounding. Currency selection is a label only; there is no FX conversion or live price lookup. Taxes, delivery, labor, preparation supplies and primer are excluded. Package types should represent the same usable paint product and coverage assumptions; the model cannot verify that.
A 5 × 4 × 2.5 m room has 2 × (5 + 4) × 2.5 = 45 m² of walls and a 20 m² ceiling. For Walls only, a measured 1 × 2 m opening leaves 43 m². Two coats give 86 m² of coated area. At an explicitly entered illustrative coverage of 10 m²/L, paint before extra is 8.6 L. Selecting 10% extra produces a 9.46 L purchase target. These are example inputs, not recommended coverage or extra.
If you enter 2.5 L packages at 20 USD and 5 L packages at 50 USD, both four smaller packages and two larger packages provide 10 L, leaving 0.54 L. Least unused chooses two 5 L packages because the package count is smaller, costing 100 USD. Lowest entered price chooses four 2.5 L packages at 80 USD. Coverage, sizes and prices start blank in the controls.
Canonical bounds: 1–20 rooms; 0–50 openings per room; labels at most 40 single-line characters; room length/width 0.1–100 m and height 0.1–20 m; opening width 0.01–100 m and height 0.01–20 m. Opening area must not exceed gross wall area. Coats must be an integer 1–10; coverage 0.01–1,000 m²/L equivalent; selected extra 0–100%.
Project painted area is bounded at 1,000,000 m², coated area at 10,000,000 m², paint before extra at 1,000,000,000 L and purchase target at 2,000,000,000 L. Package types: 0–6; volume 0.05–100 L equivalent; optional price 0–1,000,000 currency units. Optimizer limits are separate from paint calculation bounds. These are computational limits, not project guidance.
Inputs use finite plain decimals of at most 32 characters. Fractions, exponents, grouping commas and expressions are rejected. Blank coverage preserves area but cannot produce a paint quantity. Invalid geometry pauses the main result; invalid package entries pause packages only. Zero paint is valid when wall openings exactly equal a wall-only room’s gross area. Labels render as escaped text.
The model assumes rectangular rooms, uniform wall height, one product coverage rate and common coats across the project. It does not detect overlapping measurements or model irregular surfaces, trim, different colors or differing products. Actual coverage and purchases may differ from the arithmetic estimate.
Primer requirements and coverage depend on the product and surface. This calculator does not assume primer quantity, primer coverage or that primer replaces a paint coat. Check the product’s preparation instructions separately; no automatic primer estimate is added.
Copy Estimate includes accepted room surfaces, area, coats, coverage, extra, paint quantity, available package comparisons, entered-price cost and limitations. Clipboard failure provides a labeled manual-copy textarea. Print Estimate opens the browser print dialog, retaining results, room/opening arithmetic, packages, cost and limitations.
Reset restores one 12 × 15 × 8 ft Walls room, two coats, Smooth context, zero extra, blank coverage and no openings or packages. It clears pricing, labels, feedback and validation errors and focuses room length. Calculations and project inputs stay in component memory unless you explicitly copy or print. No accounts, location, storage, analytics, Share, URL state or calculation networking is used.
Choose the surfaces, enter measured dimensions and openings, then enter coats and your product’s coverage per coat. The combined coated area divided by coverage gives paint before your selected extra. No coverage is assumed.
Walls use 2 × (length + width) × height minus measured openings. Ceiling uses length × width. Both adds them. All rooms are rectangular with uniform wall height.
Enter their measured width and height if those wall areas will not be painted. Deduct only the area appropriate to your project. Openings never reduce ceiling area and cannot exceed gross wall area.
Coated area multiplies the combined painted area by 1–10 whole coats. With the same per-coat coverage, twice the coats requires twice the modeled paint before extra. Primer is excluded.
Coverage is a product and application assumption, not a universal constant. Enter the per-coat rate you are working with in m²/L or ft²/US gallon; switching units converts that physical rate.
No. Surface labels are context only. Use the product’s coverage and preparation information for the surface involved; no hidden numerical penalty is applied.
It increases paint before extra by your selected 0–100%. The default is zero, and none of the shortcuts is a universal recommendation or mandatory waste factor.
It searches bounded whole-number combinations of up to six entered sizes. Least unused minimizes overage, then package count and input order. If search limits are reached, paint remains available without a partial optimum.
Least unused minimizes excess volume. Lowest entered price minimizes cost and needs every option’s price, including explicit zeros. A cheaper combination may contain more packages or more unused paint; both results appear when different.
No. Primer quantity and coverage depend on the product and surface, and primer is not assumed to replace a paint coat. This estimate covers only the paint coats and coverage you enter.
Reviewed September 27, 2026. NIST: SI conversion factors, Appendix B.8 (opens in a new tab) documents the length and volume units. The model derives exact volume factors from the base definitions. This review covers geometry, unit conversion and the bounded package search; no universal product coverage or surface-factor dataset is used.