How to use Aspect Ratio Calculator
- Type the ratio as two numbers, such as 16 and 9.
- Choose whether the measurement you already have is the width or the height.
- Type that measurement in the known side value, and set the decimal places for a fractional answer.
- Optionally add breakpoint,width pairs in pixels, one per line, to get a height for each supplied width.
- Read the missing side in the answer, then check the formula line to see the multiplication behind it.
Example: Aspect Ratio Calculator
Work out the height of a 16:9 frame from its width.
Options
- Ratio width and ratio height
- The two numbers that describe the shape, for example 16 and 9. Each one accepts 0.000001 to 100000, and the calculator refuses a side of zero or below.
- Which side do you know?
- This tells the calculator which ratio number matches your measurement, so it divides by the other one.
- Known side value
- The measurement you already have, in pixels or in any other single unit. The answer comes back in that same unit, up to 1000000.
- Decimal places
- 0, 2 or 4. The setting rounds an answer that does not divide evenly, and a whole answer prints with no decimal point.
- Breakpoint widths
- Enter breakpoint,width pairs such as 375,320 and 1440,1280. A 16:9 ratio gives heights 180 and 720 for those supplied widths. The breakpoint is a label for your layout; it does not automatically measure the available width.
Supported inputs and limits
Where your input is processed
This tool processes your input in this browser. Your text and files are not uploaded to UseFreeTools. Check this tool's limits for anything it may save on your device.
Where the multiplication comes from
A ratio such as 16:9 says the width divided by the height equals 16 divided by 9. When the width is the known side, the height follows from the width multiplied by 9 and then divided by 16. Rearranged the same way, it gives the width from the height. Dividing once at the end keeps the answer from drifting the way it would if a rounded figure were divided again.
Rounding to whole pixels
A screen or a video frame stores whole pixels, so a height of 1080.25 has to become 1080 or 1081. Rounding moves the true ratio a little, and the gap grows with size. When an exact match matters, keep the side you know fixed and round only the missing side, then compare the pair against the ratio you started with.
Questions about Aspect Ratio Calculator
What does a 16:9 ratio mean?
The first number is the width and the second is the height, both measured in the same unit. A 16:9 frame is 16 units wide for every 9 units high, so 1920 wide gives 1080 high.
Can the ratio sides be decimals?
Yes. A ratio of 1.5:1 works the same way as 3:2, because only the relationship between the two numbers matters. Decimals are read exactly, not rounded first.
Why does my answer have decimals?
Not every ratio and size divide evenly. Set Decimal places to 4 for a closer figure, or keep 2 for a practical measurement.
Does this change my image?
No. The calculator works with the numbers you type. It never opens, resizes or saves a picture, and nothing leaves your browser.