Formula
g = gcd(W, H) · ratio = W/g : H/g
Scale decimals to integers when necessary, compute the greatest common divisor, then divide both dimensions by it.
Image & screen
● Runs locallyAspect Ratio Calculator
Turn width and height into a reduced, unitless aspect ratio. Integer dimensions use an exact greatest common divisor; decimals are rationalized to a controlled nine-place scale before simplification.
Example values
Simplified aspect ratio
Assumptions
- Decimal inputs use at most nine fractional places for rationalization.
- A common ratio is labelled near only within 0.5% relative difference.
The ratio is unitless as long as width and height use the same unit.
Formula review
Formula v1.0.0
Reviewed 2026-08-03
CalcFlow engineering review
Aspect Ratio Calculator: Worked example
gcd(1920, 1080) = 120. Dividing both values by 120 gives 16:9, with a decimal quotient of 1.777778.
Frequently asked questions
What does 16:9 mean?
For every 16 equal width units there are 9 equal height units. It does not prescribe a pixel resolution.
Can I enter centimetres instead of pixels?
Yes, when both dimensions use the same unit. The resulting ratio is unitless.
Why is a ratio marked near?
The exact quotient is close to a recognized common ratio but is not mathematically identical.