Video File Size Calculator

You need a five-minute 1080p clip under 25 MB for email. Should you export at 2 Mbps or drop to 720p? A quick estimate saves another round of trial exports. These numbers are planning tools, not guarantees. Always export a short sample before a long render.

When the destination lists a hard megabyte cap, you can also compress video to a target size on Mac or on Windows instead of iterating bitrate by hand.

What you need to estimate size

Four inputs drive most delivery files:

Input	Example
Duration	300 seconds
Video bitrate	5 Mbps
Audio bitrate	0.128 Mbps (128 kbps)
Container overhead	Small; often ignored for planning

Codec choice (H.264 vs HEVC) changes how many Mbps you need for the same look. It does not change the formula.

If you already have a clip, reverse the math to learn its average bitrate: (MB × 8) ÷ seconds. That helps when you want to copy settings from a known good upload.

The core formula

Size (bits) ≈ (video bitrate + audio bitrate) × duration

Convert to megabytes:

MB ≈ (video Mbps + audio Mbps) × seconds ÷ 8

Example:

• Video: 8 Mbps
• Audio: 0.128 Mbps
• Duration: 120 s

(8.128 × 120) ÷ 8 ≈ 122 MB

Add about 1 to 3 percent for container overhead if you are cutting close to a hard cap.

Reverse the formula when you have a cap: allowed Mbps ≈ (MB × 8) ÷ seconds. For 25 MB and 120 s, total bitrate is about 1.67 Mbps, which usually means 720p (or a shorter clip) for acceptable quality. Email caps vary by provider; see email attachment size limits .

Related: how long is a 10 MB video .

Quick reference tables

Approximate size for H.264 video plus 128 kbps audio:

Duration	2 Mbps	5 Mbps	8 Mbps
30 s	~8 MB	~19 MB	~30 MB
1 min	~16 MB	~38 MB	~61 MB
5 min	~77 MB	~192 MB	~307 MB
10 min	~154 MB	~384 MB	~614 MB

1080p talking-head content often looks acceptable between 4 and 8 Mbps. Screen recordings with small text may need higher Mbps at the same resolution, or a 720p export instead.

Leave 5 to 10 percent headroom under a hard cap. Upload widgets and operating systems do not always count megabytes the same way. Round down when the form says “10 MB max.”

Resolution and frame rate multipliers

No multiplier is exact because content complexity matters. These are planning ranges:

Change	Size impact (typical)
1080p to 720p	About 40 to 55 percent smaller at a similar quality target
4K to 1080p	Much smaller pixel count; often a large saving
60 fps to 30 fps	Up to about 40 to 50 percent smaller at similar quality settings
H.264 to HEVC at the same look	Often about 30 to 50 percent smaller

See frame rate in video and H.264 vs H.265 .

Audio bitrate to include

Do not forget audio when the cap is tight.

Audio setting	Bitrate
Voice mono	64 to 96 kbps
Voice stereo	96 to 128 kbps
Music	160 to 192 kbps

128 kbps AAC adds about 1 MB per minute. On a 10 MB budget that matters. Do not strip speech to unusable levels just to shave one megabyte off video.

From estimate to actual export

1. Pick target MB and duration, then solve for Mbps.
2. Choose a resolution and codec that can look good at that Mbps.
3. Export a 10-second sample at those settings.
4. Scale: sample MB × (total duration ÷ sample duration).
5. Adjust quality up or down, or trim more.

If the math says 2 Mbps at 1080p but text looks soft, trim more or accept 720p instead of crushing bitrate again.

For export walkthroughs: compress video on Mac or on Windows . For platform ceilings, see YouTube video size limits . Bitrate concepts: what is video bitrate .

When a calculator is enough

A napkin estimate can work when you are choosing between 720p and 1080p, or checking whether a five-minute clip can ever fit a 25 MB email cap before you edit.

When the form lists an exact megabyte number and you compress the same kind of clip often, skip the spreadsheet. In GetCompress , set a video target file size, preview the result, and reuse a preset. Exact target size is a video workflow only. The calculator still helps you decide whether the job is realistic before you spend time on a long encode.