Ratio & proportion tools
Equivalent Ratio Calculator
Complete an equivalent ratio such as 2:3 = 10:? and see the multiplier behind it.
Leave exactly one box empty — that is the value SnapRatios will find.
2 : 3 = 10 : ?
Exact result
15
D = 15 · completed proportion 2 : 3 = 10 : 15
Working
- Cross-multiply: d = (b × c) ÷ a
- 3 × 10 = 30
- 30 ÷ 2 = 15
Equivalent ratios
| Multiplier | Ratio |
|---|---|
| ×1 | 2 : 3 |
| ×2 | 4 : 6 |
| ×3 | 6 : 9 |
| ×4 | 8 : 12 |
| ×5 | 10 : 15 |
| ×6 | 12 : 18 |
One factor, applied to every part
Two ratios are equivalent when one is the other with every part multiplied — or divided — by the same non-zero factor. Nothing else counts: adding 4 to both parts of 2:3 gives 6:7, which is a different relationship entirely.
2:3 scaled by 4
2 × 4 = 8 and 3 × 4 = 12, so 2:3 = 8:12.
Proof: 8/12 = (2 × 4)/(3 × 4) = 2/3, because the factor 4 cancels top and bottom.
Reverse it: 8 ÷ 4 = 2 and 12 ÷ 4 = 3, which is why 2:3 is the simplest form of 8:12.
| Factor | Equivalent form | As a quotient |
|---|---|---|
| ×1 | 2:3 | 2 ÷ 3 = 0.666… |
| ×4 | 8:12 | 8 ÷ 12 = 0.666… |
| ×5 | 10:15 | 10 ÷ 15 = 0.666… |
| ×0.5 | 1:1.5 | 1 ÷ 1.5 = 0.666… |
Every equivalent form of 2:3 has the same quotient — that identical quotient is the definition.
Equivalent ratio or proportion — which do you need?
| What you have | What you want | Tool |
|---|---|---|
| A ratio and a scale factor | Another form of the same ratio | This page |
| 2:3, need it in fifteenths | 10:15 | This page |
| Three of the four values in a : b = c : d | The missing fourth value | Proportion calculator |
| 1:25,000 and a 3.4 cm measurement | The real distance | Proportion calculator |
The two are the same algebra approached from different directions. An equivalent ratio starts from a known factor and produces new numbers; a proportion starts from known numbers and recovers the factor implicitly through cross-multiplication. If you already know what to multiply by, stay here.