Calculating your uncompressed size is straightforward once you know the Image Size from Dimensions formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Image Size from Dimensions Calculator.
What is Image Size from Dimensions?
The Image Size from Dimensions calculation tells you your uncompressed size from a few simple inputs. The figure you are solving for here is the uncompressed size.
The Image Size from Dimensions formula
The core formula is:
Uncompressed size = Width × Height × Bits per pixel ÷ 8 ÷ 1048576Here is what each input means:
- Width — a value measured in px. Example: 1,920 px.
- Height — a value measured in px. Example: 1,080 px.
- Bits per pixel — a number. Example: 24.
How to calculate it step by step
- Write down the width (for example, 1,920 px).
- Write down the height (for example, 1,080 px).
- Write down the bits per pixel (for example, 24).
- Apply the formula above to get your uncompressed size.
- Double-check the result with the Image Size from Dimensions Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Width | 1,920 px |
| Height | 1,080 px |
| Bits per pixel | 24 |
| Uncompressed size | 5.93 |
| In bytes | 6,220,800 |
With width of 1,920 px, height of 1,080 px and bits per pixel of 24, the uncompressed size works out to 5.93.
Example 2
With width of 3,800 px, height of 1,080 px and bits per pixel of 24, the uncompressed size works out to 11.74.
| Result | Value |
|---|---|
| Uncompressed size | 11.74 |
| In bytes | 12,312,000 |
Example 3
With width of 960 px, height of 1,080 px and bits per pixel of 24, the uncompressed size works out to 2.97.
| Result | Value |
|---|---|
| Uncompressed size | 2.97 |
| In bytes | 3,110,400 |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
Prefer not to do the maths by hand? — the Image Size from Dimensions Calculator does it instantly, for free, with the formula and a worked example built in.
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