Use this free Ratio Calculator to simplify ratios (A:B), convert ratios to “A to B”, see each part as a percent of the whole, and scale the ratio to any size (perfect for recipes, mixtures, map scales, screen sizes, business comparisons, and more).
Type two numbers (decimals allowed). We’ll simplify the ratio, show the “A to B” form, and calculate each part’s share of the whole. You can also scale the ratio to match a target value (e.g., scale a recipe from 2:3 to make 30 servings).
A ratio compares two quantities by division. If you have values A and B, the ratio is written as A:B (read “A to B”). The core idea is simple: two ratios are equivalent if they reduce to the same fraction.
Mathematically, the ratio A:B is equivalent to the fraction A/B (as long as B ≠ 0). When you “simplify” a ratio, you are dividing both sides by the same factor so the numbers become smaller but the comparison stays identical.
If you multiply or divide both parts of a ratio by the same non-zero number, you get an equivalent ratio:
To simplify integer ratios, we divide by the greatest common divisor (GCD) of A and B. The GCD is the largest integer that divides both. For example, for 20:30, the GCD is 10, so:
Real life often uses decimals: 1.5:2.25 (measurements, money, weights). A common strategy is to scale both numbers by a power of 10 to remove decimals, then simplify. Example:
That’s exactly what this calculator does behind the scenes: it finds the maximum number of decimal places, scales both parts to integers, simplifies, then formats the final ratio.
Here are practical examples that match what people search for most—so they’re also great for explaining the tool when you share it.
You have A=18 and B=24. The simplified ratio is 3:4 because GCD(18,24)=6 and 18÷6 = 3, 24÷6 = 4.
Your recipe is 2:3 (2 cups flour : 3 cups milk). You want the flour to become 10 cups. The scale factor is 10 ÷ 2 = 5. So milk becomes 3 × 5 = 15. Scaled ratio: 10:15 (still simplifies back to 2:3).
Suppose you split effort in a project: A=4 hours, B=6 hours. Total is 10 hours. A’s share is 4/10 = 40%. B’s share is 6/10 = 60%. This is useful when you want to describe “how much of the whole” each part is.
A 1920×1080 screen is 1920:1080. Divide both by 120 to simplify → 16:9. That’s why 16:9 is the standard “widescreen” ratio.
A scale of 1:24,000 means 1 unit on the map equals 24,000 of the same units in real life. If 1 inch on the map equals 24,000 inches in real life, that’s 2,000 feet (because 24,000 ÷ 12 = 2,000).
When you click Calculate Ratio, the tool produces a few different “views” of the same relationship. The goal is to give you the most common formats people need in real situations—without forcing you to do extra conversions.
You’ll see the simplest integer ratio like 2:3. This is the “cleanest” way to communicate a comparison. It’s perfect for writing down a mixture (“2 parts blue, 3 parts yellow”), describing an aspect ratio (“16:9”), or communicating a proportion quickly (“3:5 split”).
Some people prefer reading ratios as words: 2 to 3. This is the same as 2:3, but it’s more natural in conversation or when explaining steps to someone else.
The ratio also corresponds to the fraction A/B. As a decimal, this is A ÷ B. For 2:3, the decimal is 0.666…. This is useful when you’re comparing “how many times bigger” A is relative to B.
If A and B are parts of a total, the calculator also shows A% and B% of the whole where: A% = A/(A+B) and B% = B/(A+B). This is perfect for splitting budgets, time, calories/macros, or group responsibilities.
The “Scale so A becomes…” mode answers: if we keep the same ratio, what should B be when A is fixed? The steps:
The “Scale so B becomes…” mode does the mirror image. This is why ratios are a cheat code for resizing anything: you’re just multiplying both sides by the same scale factor.
Edge cases: If A=0 and B=0, the ratio is undefined. If only one side is 0, the ratio simplifies to 0:1 or 1:0 (depending on which side is zero).
A ratio compares two quantities by division. It tells you how many units of one thing exist per unit of another. Ratios are commonly written as A:B or “A to B”.
Divide both parts by their greatest common divisor (GCD). For decimals, multiply both parts by a power of 10 to remove decimals first, then simplify.
Yes. 4:6 simplifies to 2:3 by dividing both sides by 2. They represent the same relationship.
If A and B are parts of a combined total, A’s percent of the whole is A/(A+B) × 100. This is useful for splits (budgets, time, ingredients).
They can, but be careful. A ratio is most interpretable when both parts represent the same kind of measurement (e.g., grams to grams). If units differ (e.g., dollars to hours), the ratio is still valid but means “dollars per hour” and is closer to a rate than a pure ratio.
Some people type values in the opposite order of what they intend. If you meant “B to A” instead of “A to B”, swap the inputs. The calculator always treats the first input as Part A and the second as Part B.
Picked from the Math & Conversion category list to maximize usefulness and internal linking.
If you want this calculator to spread, you need people to use it in a “challenge” format. Here are a few prompts that naturally generate shares and screenshots:
Pro move: post your result image + link, then ask friends to reply with theirs. That’s the easiest “loop.”