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Aspect Ratio Calculator

Updated · Standard formula, shown below

Aspect ratio (width ÷ height) 1.7778
New height at the same ratio
720 px
Result
Original size
2.07 megapixels
Result
Original width
1920 px
You entered

This calculator works out the aspect ratio of a picture, screen or video and resizes it without stretching. Enter the original width and height and a new width, and you get the ratio, the matching new height and the megapixel count.

Formula

Aspect ratio = width ÷ height. To keep it when resizing, new height = new width × height ÷ width. Megapixels = width × height ÷ 1,000,000.

  • w, h: original width and height (pixels, inches or any unit, both the same)
  • nw: the new width in the same unit

Worked Example

A 1920 × 1080 video resized to 1280 wide.

  1. 1920 ÷ 1080 = 1.7778, which is 16 ÷ 9 (16:9)
  2. New height = 1280 × 1080 ÷ 1920 = 720 px
  3. 1920 × 1080 = 2,073,600 pixels = 2.07 megapixels

Limits and common mistakes

  • Common ratios as decimals: 4:3 = 1.3333, 3:2 = 1.5, 16:10 = 1.6, 16:9 = 1.7778, 21:9 ≈ 2.3333.
  • Round the new height to a whole pixel; video encoders often need an even number.
  • A screen size in inches is the diagonal, not the width.
  • To find the new width for a target height instead, use new width = new height × width ÷ height.
  • Printing: a 3:2 photo printed 6 in wide is 4 in tall; a 4:3 photo at 6 in wide is 4.5 in tall and gets cropped on 6 × 4 paper.
Formula used
in w | Original width | px | 1920 | 0
in h | Original height | px | 1080 | 0
in nw | New width | px | 1280 | 0
out r | Aspect ratio (width ÷ height) | - | w / h | 4
out nh | New height at the same ratio | px | nw * h / w | 0
out mp | Original size | megapixels | w * h / 1000000 | 2

Each line is one input (in, sel, list) or one result (out: label, unit, formula, decimals). How the calculators work

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.