Ratio Calculator

Ratio Calculator does two jobs. The Ratio tab finds the missing term in a proportion A:B = C:D when you know any three of the four numbers. The Ratio Scaling tab multiplies or divides both sides of a ratio by a scale factor.

Ratio tab
Enter exactly three of A, B, C and D and tap Calculate. The app fills in the fourth. For example, a 2:3 mix with 8 cups of the first ingredient needs 12 cups of the second: 2 : 3 = 8 : 12.

Ratio Scaling tab
Enter a ratio, a scale factor, and choose enlarge or shrink. 250:280 enlarged 2.5 times is 625:700. Shrinking divides both parts by the factor, so 250:280 shrunk 2.5 times is 100:112.

Where it helps
• Scaling a recipe up for more guests, or down for fewer
• Mixing paint, concrete, fuel or cleaning solution at a set strength
• Resizing a photo, drawing or map while keeping its proportions
• Splitting a budget or a batch in a fixed ratio
• Checking the ratio of two sides on a plan

Good to know
• The Ratio tab needs exactly three values; leave one box empty
• Zero is rejected in the Ratio tab, because a ratio term cannot be zero
• Use a scale factor such as 2, 2.5 or 0.5

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