Ratio Calculator
Simplify a ratio to lowest terms and scale it up or down.
Quick answer
- Formula: Simplified ratio = (a ÷ GCD) : (b ÷ GCD); Scaled ratio = (a × k) : (b × k)
- Worked example — Simplified ratio: 2:3 (full example below).
Ratio Calculator
| Simplified ratio | 2:3 |
| Simplified a | 2.00 |
| Simplified b | 3.00 |
| Scaled ratio | 16:24 |
| a ÷ b as a decimal | 0.6667 |
| Total parts (a + b) | 20.00 |
8:12 simplifies to 2:3 (both sides divided by the GCD, 4). Scaled by 2, the original ratio becomes 16:24 — a different size, but exactly the same proportion.
A ratio compares two quantities, written a:b. Simplifying a ratio works exactly like simplifying a fraction: divide both sides by their greatest common divisor, so 8:12 becomes 2:3.
Enter the two parts and a multiplier to scale the ratio — useful for recipes, screen dimensions, map scales and mixing quantities, where the proportions must stay the same while the amounts change.
The formula
Worked example
8:12 simplifies to 2:3 (both sides divided by the GCD, 4). Scaled by 2, the original ratio becomes 16:24 — a different size, but exactly the same proportion.
The example is pre-loaded in the result panel — press Calculate with your own numbers to replace it.
Frequently asked questions
How is a ratio different from a fraction?
A fraction like 2/3 describes part of one whole. A ratio like 2:3 compares two separate quantities — 2 parts of one thing to 3 parts of another — so the whole is actually 5 parts.
How do I split an amount using a ratio?
Add the parts to get the total, divide the amount by that total, then multiply by each part. Splitting $100 in a 2:3 ratio: $100 ÷ 5 = $20 per part, giving $40 and $60.
Category: Math calculators
Sources & methodology
This calculator applies the formula shown on this page exactly as written, using the standard definitions for its inputs. Results are computed from the values you enter — no data is stored — and are rounded only for display.
Content last reviewed by CalcHub Editorial.
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