What is a Ratio & Proportion Calculator?
The ratio calculator solves proportions of the form A:B = C:X for an unknown value, and simplifies ratios between two numbers. It is used for scaling recipes, map scales, and mixing ratios.
How it's calculated
A : B = C : X → X = B × C ÷ A
This uses the fundamental property that the product of the means equals the product of the extremes.
Good to know
- A map scale of 1:100,000 means 1cm on the map equals 100,000cm in reality. The larger the second number, the more zoomed-out the map is.
- The golden ratio (about 1:1.618) is often claimed to appear throughout art and nature, but many famous examples are disputed as retroactive pattern-matching rather than intentional design.
- Standard paper's 1:√2 ratio is far more practically useful — folding it in half preserves the same ratio, which is why A4, A3, and A5 all scale cleanly into each other.
- Construction and chemistry often communicate purely in ratios, like a 1:2:4 concrete mix (cement:sand:gravel), because the properties hold regardless of total batch size.
- Map scale terminology is counterintuitive: 1:5,000 is a 'large-scale' map (detailed), while 1:500,000 is 'small-scale' (broad coverage) — the opposite of what the numbers might suggest.
Frequently asked questions
Q. What is the difference between a ratio and a proportion?
A ratio compares two quantities (3:2); a proportion (or percentage) expresses how much one is relative to a reference (1.5, or 150%).
Q. Which shows more detail, a 1:100 or 1:50 scale drawing?
1:50. The same object is drawn larger, showing finer detail.
Q. How do I scale a recipe up by 1.5x?
Multiply every ingredient by 1.5. Leavening agents like salt or baking powder are often kept slightly below strict proportion for best results.