Enter values and select Calculate.
Calculated result
Calculation steps
Find an aspect ratio from width and height
Enter any width and height above to reduce the dimensions to their simplest aspect ratio, such as 1920 × 1080 becoming 16:9.
Resize dimensions without changing the aspect ratio
Enter a new width or height to calculate the matching dimension while preserving the original proportions.
Formula and worked example
Aspect ratio = width:height reduced by their greatest common divisor. New height = new width × original height / original width, and the inverse solves a new width.
1920 × 1080 divides by 120 to become 16:9. At a new width of 1280, the matching height is 1280 × 1080 / 1920 = 720.
Calculations use full internal precision and trim insignificant trailing zeros for display. Confirm any rounding rule required by a course, workplace, publication, or technical standard.
How to use it
Enter the original width and height in the same unit.
Calculate to see the simplified ratio and decimal relationship.
To resize proportionally, choose whether to solve for width or height and enter the other new dimension.
Round a calculated pixel dimension only when the destination format requires whole pixels.
Images, screens, and video
The same proportional math applies to images, screens, video frames, printed rectangles, and layout boxes.
Pixels are a common input, but identical pixel dimensions do not imply identical physical display sizes.
Common ratios such as 1:1, 4:3, 3:2, 16:9, 9:16, and 21:9 are examples, not the only valid ratios.
Precision and interpretation
Integer dimensions use exact greatest-common-divisor reduction.
Decimal dimensions are normalized to a practical exact ratio within six decimal places.
Both dimensions must be greater than zero; zero and negative dimensions are rejected.
Methodology and limits
This deterministic calculator uses the formula shown above and strict finite-number parsing. It does not evaluate expressions, execute entered text, call a remote calculation service, or claim to replace instruction or professional review.