Video File Size Estimator

How to use

Know how much storage your video needs before you hit record. Estimate size from modeled or entered bitrate, or find how long fits in available storage.

Choose File Size to enter hours, minutes and seconds, or How Long Fits to enter available nominal storage. Simple selects an illustrative bitrate from resolution, frame rate, codec and quality; Bitrate accepts video and audio rates directly. Optional quick-load settings are editable starting points. Storage headroom defaults to 10% as a planning example. Compare settings uses the current settings as A and a separate Simple or Bitrate setting B, at the same duration. Show calculation starts closed. Copy Result and Reset operate locally; refresh clears settings.

Video file-size formula

Total media bitrate B (Mbps) = video bitrate V (Mbps) + audio bitrate A (kbps) / 1000. For duration T seconds: media bytes = B × 1,000,000 × T / 8; decimal GB = B × T / 8000.

1 Mbps = 1,000,000 bits per second and 1 byte = 8 bits. Therefore 1 MB/s = 8 Mbps, not 1 Mbps. A bitrate measures bits over time; file size measures accumulated bytes.

Final modeled bytes = media bytes × (1 + container planning allowance/100). Suggested free space = final modeled bytes × (1 + storage headroom/100). The container allowance is separate from storage headroom.

Bitrate and file size

For a known average encoded bitrate, size grows linearly with duration. Twice as much recording time at the same total bitrate means twice the media bytes. Resolution, frame rate, codec and quality do not uniquely determine compressed video size. This calculator never applies an extra pixel-count or frame-rate multiplier after selecting the bitrate.

For a separate transfer-capacity question, estimate bandwidth for a known video payload with explicit traffic, units and headroom assumptions. Encoded file size does not by itself predict streaming delivery, protocol overhead or network performance.

Simple mode vs Bitrate mode

Simple estimates a modeled average video bitrate from an explicit bounded preset table. Every supported combination has a stored bitrate and an illustrative label; unsupported selections show a message suggesting Bitrate mode rather than inventing or interpolating a rate. Selected video, audio and total media bitrate are always visible in results.

If you know the actual average encoded bitrate, Bitrate mode gives a direct size estimate from that rate and duration. For VBR, final size depends on the realized average bitrate; resolution and codec alone cannot predict scene complexity or encoded size.

For constant bitrate the rate × time arithmetic is straightforward; it does not imply that all container or filesystem bytes have been accounted for.

Video bitrate

Bitrate accepts Kbps, Mbps or Gbps using decimal SI factors. 1 Mbps = 1,000 Kbps; 1 Gbps = 1,000 Mbps. It supports zero video if audio is positive; at least one media rate must be positive. The model uses the entered or selected average bitrate as-is, with full precision before display rounding.

Bitrate Advanced offers an optional 0–20% container/muxing planning allowance, default zero. MP4, MOV and MKV have no universal overhead percentage. Real files may include metadata, multiple tracks or other data not captured by this simple allowance.

Audio bitrate

Audio contributes storage throughout the duration. Choose No audio, 128, 192, 256 or 320 kbps, or Custom. Bitrate and custom audio accept kbps or Mbps; the default 256 kbps equals 0.256 Mbps. No audio explicitly sets its rate to zero. Video and audio are added before calculating bytes; there is no hidden audio exclusion.

Resolution, FPS and codec presets

Illustrative BuzCalculator bitrate assumption, not a measured bitrate, camera specification, benchmark or universal codec standard. Resolution, frame rate, codec and quality do not uniquely determine compressed file size.

The explicit compressed-video table supports 1080p at 24–30, 50–60 and 120 fps; 1440p and 4K at 24–30 and 50–60 fps; and 8K at 24–30 fps. Those rows offer H.264 / AVC, H.265 / HEVC and AV1, each with Economy, Standard and High bitrate tiers. Frame rates within a named band intentionally use the same illustrative assumption. Other combinations are unsupported.

ProRes 422 has four illustrative Standard-tier entries: 1080p at 24–30 fps, 150 Mbps; 1080p at 50–60 fps, 300 Mbps; 4K at 24–30 fps, 600 Mbps; 4K at 50–60 fps, 1,200 Mbps. They are rounded BuzCalculator assumptions, not Apple’s exact target rates or camera guarantees. Other resolutions, 120 fps and Economy/High ProRes tiers are unsupported; selecting High does not select ProRes 422 HQ. Apple’s documentation supports the distinction between ProRes formats and their variable rates, not an endorsement of these illustrative values.

Quality tiers are rough modeled bitrate levels, not guarantees of CRF, quantizer, image quality or codec flavor. Quick presets are not YouTube upload recommendations; no platform-specific bitrate presets are included.

GB vs GiB

Decimal SI: 1 Mbps = 1,000,000 bits/s; 1 byte = 8 bits; 1 KB = 1,000 bytes; MB = 1,000,000; GB = 1,000,000,000; TB = 1,000,000,000,000; PB = 1,000,000,000,000,000. Binary 1 GiB = 1,073,741,824 bytes.

Storage manufacturers commonly label nominal capacity in decimal GB/TB. Some operating systems or tools use binary GiB/TiB-style quantities or different labels. This calculator uses decimal storage for primary results and labels the optional binary GiB detail explicitly. A smaller displayed binary number does not mean bytes have disappeared. Filesystems and existing content can also reduce available space.

Storage headroom

Storage headroom is extra space beyond modeled video size: video size × (1 + headroom/100) ≤ available storage. Reverse calculation divides capacity by that factor, rather than subtracting a reserve percentage.

Headroom ranges from 0–200%; shortcuts 0%, 10% and 20% are editable examples, not recommendations or industry requirements. Suggested free space is a planning amount, not required physical disk size. Headroom does not inflate encoded file size or per-hour media data. Container allowance can increase modeled bytes separately.

How Long Fits

How Long Fits uses the same Simple or Bitrate settings. Usable modeled video bytes = available storage bytes / (1 + headroom/100). Duration seconds = usable bytes × 8 / [total media bits per second × (1 + container allowance/100)]. Do not subtract a reserve percentage when using this extra-space headroom convention.

The displayed recording duration is theoretical under selected average bitrate assumptions. A precise secondary hours value accompanies the concise seconds/minutes/hours/days label. Coarse recording-time labels truncate rather than round capacity upward. Reverse estimates beyond 100,000 hours show a planning-bound error; no duration is capped silently.

Storage visualizer

The visual compares modeled file size with selected nominal storage: file bytes / capacity bytes × 100. Its progress bar stops at 100%, while text retains the actual percentage and states when the file or suggested free space exceeds capacity. File Size mode uses storage selection only for this context; How Long Fits uses it as available storage input.

128, 256 and 512 GB media counts use ceil(file bytes / nominal medium bytes). These are minimum counts by nominal capacity, using file size alone and assuming all nominal capacity is available; no per-medium headroom is included. They do not model formatted capacity or guarantee a single unsplit file can span multiple cards.

Comparing settings

Compare settings is an optional disclosure, not another top-level mode. Setting A follows the main inputs; B may use a Simple preset or direct Bitrate input. The duration is held constant, including when A’s duration comes from How Long Fits. Results show estimated size, size/hour, total media bitrate, container allowance, B − A bytes and percent difference relative to A.

Under these selected preset bitrate assumptions, a codec change can change modeled size; this is not a statement that H.265 is always a fixed percentage smaller than H.264. Encoder, settings, content, quality target, bit depth, chroma sampling, GOP, rate-control mode and hardware/software implementation affect actual efficiency. Unsupported B presets show an error; no fallback rate is invented.

Worked examples

One-hour bitrate estimate

20 Mbps video + 192 kbps audio = 20.192 Mbps. Multiply by 3,600 seconds and divide by 8000 to obtain 9.0864 GB, with zero container allowance.

Audio adds storage

5 Mbps video + 320 kbps (0.32 Mbps) audio = 5.32 Mbps. For one hour this is 2.394 GB, versus 2.25 GB without audio.

How Long Fits on one decimal TB

At 50 Mbps total, zero container allowance and 10% headroom, usable video bytes = 1,000,000,000,000 / 1.10 = 909,090,909,090.909. Duration = usable bytes × 8 / 50,000,000 = 145,454.545455 seconds, or 40.40404 hours (1 day 16 h).

GB versus GiB

1 GB = 1,000,000,000 bytes; 1 GiB = 1,073,741,824 bytes. One decimal GB is 0.931323 GiB. Always compare the labeled units.

Default illustrative preset

2 h 15 min = 8,100 seconds; 4K / 30 fps / H.265 / HEVC / High uses 48 Mbps video plus 256 kbps audio, total 48.256 Mbps. Estimated size = 48.8592 GB; per hour = 21.7152 GB; 10% planning headroom gives 53.74512 GB suggested free space. These are preset-based estimates, not measured recording rates.

Assumptions and limitations

Projection based on entered average bitrate assumptions. Actual encoded size may vary with encoder, settings, content, quality target, bit depth, chroma sampling, GOP, rate control and implementation. No camera-specific capacity, upload time or rendering-time guarantee.

If you know the actual average encoded bitrate, Bitrate mode gives a direct size estimate from that rate and duration. For VBR, final size depends on the realized average bitrate; resolution and codec alone cannot predict scene complexity or encoded size.

Simple settings do not predict scene complexity or actual encoder output. Audio assumes one entered aggregate audio bitrate; overhead is only a user-entered planning allowance. Nominal storage does not automatically account for formatting, existing content, reserved operating-system space or camera file limits. No video upload, file inspection, camera database, codec recommendation, upload-time estimate or rendering-time prediction is performed.

File Size duration accepts whole hours 0–999 and whole minutes/seconds 0–59, with positive total duration. Video rate is bounded at 1,000,000 Mbps equivalent; audio at 100,000 kbps equivalent; storage at 1e9 TB equivalent; headroom at 0–200%; container allowance at 0–20%. Reverse duration is bounded at 100,000 hours. Plain finite decimals and supported enum selections are required. Inputs are local and refresh clears state.

FAQ

Sources

References support unit definitions and codec terminology; they do not endorse BuzCalculator or make these illustrative preset values universal standards.

• NIST: Metric (SI) prefixes (opens in a new tab)
• NIST: Prefixes for binary multiples (opens in a new tab)
• Apple: About Apple ProRes (opens in a new tab)