Enter a width and height to see the simplified ratio, or tap a common preset. Fill in a new width or height and the other side scales automatically to match.
- Type the original width and height (for example 1920 and 1080).
- Read the simplified ratio and decimal value below the fields.
- Type a new width or height to scale the other side to the same ratio, or tap a preset button.
Aspect Ratio Calculator
Enter an original width and height and the tool simplifies the ratio down to its lowest terms (for example 1920x1080 reduces to 16:9), showing the decimal value too.
Key features
- Original width and height number inputs, prefilled with 1920x1080 and editable to any dimensions.
- A new-width and new-height pair - type into either one and the matching side scales automatically along the same ratio.
- Seven one-tap presets - 16:9, 9:16, 4:3, 3:2, 1:1, 21:9, and 5:4 - fill the width and height for you.
When to use it
It is handy for resizing an image, video frame, or design canvas without distorting it - so a photo, export, or layout keeps its original proportions at the new size.
Privacy
The width and height you type stay in the browser - the ratio is reduced on this device, with no upload and no account.
What a zero or negative width does
Aspect Ratio Calculator does not show a validation error for an out-of-range original width or height. Type 0 or a negative number into either field and the calculator quietly treats it as 1 instead of stopping the calculation, so the ratio still renders against that floor value rather than the number you actually typed, with no warning that the number was out of range.
| Original width | Original height | What renders |
|---|---|---|
| 1920 | 1080 | 16 : 9 (decimal 1.7778) |
| 0 | 1080 | 1 : 1080 (width treated as 1) |
| 1920 | -50 | 1920 : 1 (negative height treated as 1) |
Comparing preset ratios without retyping your target size
Aspect Ratio Calculator remembers which of the new-width or new-height fields you typed into last. Enter a target once, such as a new width of 1280, then click through the preset buttons one after another - the other field recalculates automatically to match whichever ratio you just picked, without you retyping 1280 each time. Switching from the default 16:9 preset to the 21:9 preset with that same 1280 new-width, for instance, recalculates the target height from 720 down to 548.57 on its own. This makes it quick to compare how the same target width looks under a square crop versus a wide frame.
Frequently Asked Questions
What does Aspect Ratio Calculator do?
It reduces a width and height to the simplest whole-number ratio (for example 3840x2160 reduces to 16:9) and can scale a new width or height to the same ratio.
Does it crop or resize my actual file?
No. This is a math-only calculator - it does not open, upload, or modify any image or video file. It just works out the numbers so you can resize elsewhere with the correct dimensions.
Why does the ratio look different from what I expected?
The tool reduces to the lowest whole-number terms using the greatest common divisor, so a slightly non-standard size (for example 1900x1069) may simplify to an unfamiliar ratio rather than snapping to the nearest common one like 16:9.
What happens if I leave the new width or new height field blank, or type 0?
A blank field does nothing - the calculator only recalculates the other side once you type a number into it. Typing 0 does compute a matching 0 for the other field, but the usual explanation line below it (for example "At width 1280, height = 720") only appears for a size greater than 0, so a 0 result shows with no sentence underneath it.
How precise is the decimal ratio value?
The decimal value under the simplified ratio is shown to 4 digits after the decimal point (for example 1.7778 for 16:9), while the simplified ratio itself is always displayed as whole numbers.
Is there a maximum width or height I can enter?
No. Both original-width and original-height fields accept any positive number with no enforced upper limit, so an unusually large size such as 100000 by 56250 (still a 16:9 pair) computes a valid simplified ratio and decimal value the same way a normal-sized input would - useful when checking a print or billboard dimension rather than a screen resolution.