Aspect Ratio Calculator
Calculate proportional dimensions, simplify aspect ratios, and inspect screen resolutions with live visual preview. Your work stays on this device whenever possible.
How to use Aspect Ratio Calculator
- Stay on 'Proportional Dimension Solver (W:H)' and enter the source size in 'Original Width (W1)' and 'Original Height (H1)'.
- Type a target in 'New Width (W2)' or 'New Height (H2)'; the other box updates as you type.
- Click a preset pill such as 4:5 or 9:16 to load a common shape.
- Switch to 'Ratio Simplifier & Screen Specs' to reduce an 'Image / Screen Width' and 'Image / Screen Height' pair.
- Read 'Decimal Ratio', 'Total Megapixels' and 'CSS Padding-Top', or press 'Apply' in the standard-resolutions table.
Worked example
Enter W1 = 1920 and H1 = 1080, then type 1000 in 'New Width (W2)'. The height box fills with round(1000 × 1080 ÷ 1920) = round(562.5) = 563. The badge shows 16 : 9, Decimal Ratio 1.78 : 1, CSS Padding-Top 56.25%, and Total Megapixels for 1000 × 563 reads 0.56 MP.
When to use this tool
- Resizing a hero image to 1000 px wide without stretching it.
- Deriving the padding-top percentage for a responsive video embed.
Important limitations
Computes exact mathematical ratios using the Euclidean greatest common divisor algorithm. Non-standard sensor or monitor resolutions with fractional pixel dimensions are rounded to the nearest integer pixel.
Comparing alternatives
Other options for aspect ratio calculator include Andrew Hedges, Digital Citizen, CalculatorSoup, Omni Calculator.
ToolkitPoint is not affiliated with those services.
Frequently asked questions
What is the CSS Padding-Top figure?
It is height ÷ width × 100 for the original ratio, for example 56.25% for 16:9. Setting that as top padding on a wrapper reserves a responsive box of the same shape.
Why can the new size be off by a pixel?
New dimensions are rounded to whole pixels, so 1000 wide from 1920 × 1080 gives 563 tall (562.5 rounded up). Pick sizes from the table if you need an exact ratio.
Why does an odd size list other resolutions?
The table matches exact reduced ratios and anything within 1.5 percent. 1366 × 768 reduces to 683 : 384, yet it still lists the 16:9 rows because it is that close.
Is my photo uploaded when I drop it?
No. The dropped image is opened locally through an object URL only to read its pixel width and height, and those two numbers then fill the fields. The picture itself is never sent anywhere.
What ratios are on the preset pills?
The pills cover 16:9, 9:16, 4:3, 1:1, 21:9, 4:5, 3:2 and 2:3. For any other shape, type the two dimensions into the fields and the tool derives the reduced ratio for you.