Aspect Ratio Calculator
Find the simplified aspect ratio of any width and height, then resize while keeping the exact same proportions.
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Reduced ratio 16 : 9 — decimal 1.78
- 1
GCD of dimensions
GCD(1,920, 1,080) = 120Greatest common divisor — the largest integer that divides both dimensions exactly. - 2
Decimal ratio
1,920 ÷ 1,080 = 1.7778 - 3
Reduced height b
1,080 ÷ 120 = 9 - 4
Reduced width a
1,920 ÷ 120 = 16
How does this calculator work?
Aspect ratio is width:height reduced by their greatest common divisor — 1920×1080 becomes 16:9. Enter both original dimensions to get the simplified ratio and decimal W/H. To resize, supply one target dimension and the tool solves the other from the original proportion so the image keeps its exact shape.
Formula
How this is calculated
Enter the original width and height. The calculator divides both by their greatest common divisor (GCD) to produce the simplest whole-number ratio a:b — for example 1920×1080 reduces to 16:9. It also reports the decimal ratio W ÷ H, which is handy when a ratio is not a clean fraction.
To resize, type either a target width or a target height and leave the other blank. The missing dimension is solved from the original proportion: a new height equals new width × (H ÷ W), and a new width equals new height × (W ÷ H). This guarantees the resized rectangle has the identical shape, just scaled.
Widths and heights are treated as positive numbers (pixels by default, but any consistent unit works). Zero or negative sizes are rejected because a ratio is undefined. Decimal inputs are allowed; the reduced a:b is rounded to the nearest whole numbers for readability, while the decimal ratio stays exact.
Frequently asked questions
Any size where width ÷ height = 16 ÷ 9 ≈ 1.778, such as 1280×720, 1920×1080, or 3840×2160. Enter one dimension and leave the other blank to get the matching value.
The width and height are divided by their greatest common divisor. For 1920 and 1080 the GCD is 120, giving 16:9.
Yes. The decimal ratio (W ÷ H) is always exact, and the whole-number a:b is the closest clean approximation.
Also known as
TG we-Calculate Editorial Team. (2026). Aspect Ratio Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/aspect-ratio-calculator
TG we-Calculate Editorial Team. "Aspect Ratio Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/aspect-ratio-calculator.
TG we-Calculate Editorial Team, "Aspect Ratio Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/aspect-ratio-calculator
@misc{wecalculate_aspect_ratio_calculator, title = {Aspect Ratio Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/aspect-ratio-calculator}}, year = {2026}, note = {TG we-Calculate} }
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