# Video File Size Calculator

URL: https://speedycalculator.com/calculators/other/video-file-size/
Last updated: 2026-10-25

> The video file size calculator estimates how much storage a video needs from its bitrate and duration, and how long a recording fits on a card of a given size.

## Inputs

- Bitrate (Mbit/s, kbit/s, Gbit/s)
- Duration (min, s, h)
- Card or drive size (GB, TB)

## Results

- File size
- Recording time on card

## Formula

```
File size = bitrate × duration ÷ 8
```

## Explanation

Bitrate, not resolution alone, determines file size. 4K at 100 Mbps fills storage about four times faster than 25 Mbps.

### How to use the Video File Size Calculator

- **Bitrate**
- **Duration**
- **Card or drive size**
- Want to work backwards? Type a value into **File size** and **Duration** is calculated for you.

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Multiply the total bitrate (video plus audio) by duration in seconds and divide by 8 to get bytes.

### Inputs explained

FieldWhat to enterBitrateUnits: Mbit/s, kbit/s, Gbit/sDurationUnits: min, s, hCard or drive sizeUnits: GB, TB

### What each result means

- **File size** = [Bitrate]×[Duration]÷8
- **Recording time on card** = [Card or drive size]×8÷[Bitrate]

### Example values

How the main result changes when **Duration** changes and everything else stays at the example values above:

Duration (min)File size (MB)51,8757.52,812.5103,75012.54,687.5155,625207,500

## Worked example

Inputs — Bitrate: 50 Mbit/s; Duration: 10 min; Card or drive size: 128 GB.

Results — **File size = 3,750 MB**; Recording time on card = 5:41:20.

## FAQ

**What bitrate does YouTube recommend for 4K?**
About 35–68 Mbps for 4K at 24–60 fps (SDR).

**Why is my file smaller than predicted?**
Variable bitrate encoders use less data for simple scenes.

**What formula does the Video File Size Calculator use?**
File size = bitrate × duration ÷ 8.

**Can I work backwards from the result?**
Yes. Type the result you want into File size and the calculator finds the matching duration.