Reviewed by CalcMulti Editorial Team·Last updated: ·← Percentage & Ratio Hub
To convert a ratio a:b to a percentage, use the formula: (a / (a + b)) × 100. This treats a as a part of the whole (a + b) and expresses it as a percentage. For example, 3:7 means 3 out of 10, which is 30%.
You can also convert in the other direction: to convert a percentage to a ratio, rewrite the percentage as a fraction (e.g., 40% = 40/100 = 2/5) and express the numerator and denominator as the ratio 2:3 (where the second part is 100% minus 40% = 60% = 3 parts).
This converter is useful for probability (3 wins out of 7 games = 3:7 win-to-loss ratio = 30% win rate), exam scores (correct:incorrect), mixing solutions (concentrate:water), and financial reporting.
Ratio a:b → Percentage: (a / (a+b)) × 100 | Percent p% → Ratio: p : (100−p)
| Ratio | Part A % | Part B % |
|---|---|---|
| 1:1 | 50.00% | 50.00% |
| 1:2 | 33.33% | 66.67% |
| 1:3 | 25.00% | 75.00% |
| 1:4 | 20.00% | 80.00% |
| 2:3 | 40.00% | 60.00% |
| 3:4 | 42.86% | 57.14% |
| 3:7 | 30.00% | 70.00% |
| 1:9 | 10.00% | 90.00% |
This calculator is for educational purposes only and does not constitute professional advice. Results are based on standard mathematical formulas. Always verify critical calculations with a qualified professional before making important decisions.