Ratio Calculator — Solve, Simplify, Split & Scale

Real-world use cases

• Scale a recipe from 4 servings to 6

  You have a pancake recipe written for 4 people but 6 are coming. Open the Scale mode, enter the base quantity (say 200 g flour) and a factor of 1.5 (6 divided by 4). The tool returns 300 g and shows the step 200 times 1.5 = 300. Repeat for each ingredient — 2 eggs becomes 3, 250 ml milk becomes 375 — and nothing gets lopsided because every quantity is scaled by the same factor.

• Read a map or blueprint scale bar

  A 1:25000 hiking map shows two peaks 8 cm apart. Use Solve proportion with 1:25000 = 8:x, leaving x blank. The tool cross-multiplies to x = 200000 cm = 2 km. For a 1:50 architectural drawing where a wall measures 4 cm on paper, the same proportion gives 200 cm real-world. The written step makes it easy to confirm you put the scale on the correct side.

• Mix paint, resin, or fertilizer to a ratio

  A two-part epoxy is 2:1 resin to hardener and you want 300 ml total. Use Split a total: enter 300 and the ratio 2:1. The tool adds the parts (3), divides (300 / 3 = 100 per share) and returns 200 ml resin and 100 ml hardener. Because it splits the exact total you asked for, you avoid the classic mistake of mixing 300 ml resin plus 150 ml hardener and ending up with 450 ml.

• Split a bill or bonus pool fairly

  Three people share a 1000 bonus by contribution 5:3:2. Split a total with total 1000 and parts 5:3:2 returns 500, 300, and 200, and the parts always add back to the original total — no rounding gap to argue over. The same flow divides a shared dinner bill, a freelance project fee, or rent between rooms of different sizes.

• Solve a unit-rate or conversion proportion

  If 3 kg of apples cost 12 dollars, what do 5 kg cost? Solve proportion with 3:12 = 5:x gives x = 20, with the cross-multiplication 3x = 60 shown. Students use the same mode for currency (2 USD = 14 CNY, so 35 USD = x), speed, and density problems, and the visible step doubles as a homework check.

Common pitfalls

• Lining the proportion up wrong. In a:b = c:x, a and c must be the same kind of quantity, and b and x must match too. For 3 kg = 12 dollars, write 3:12 = 5:x (kg on the left, dollars on the right), not 3:12 = x:5. The visible cross-multiplication step is there so you can catch a flipped layout before trusting the answer.

• Mixing up Split and Scale. Split divides one total into parts that add back to that total (200 as 2:3 gives 80 + 120 = 200). Scale multiplies a quantity by a factor and the result is larger or smaller than the input. Reaching for Scale when you meant Split is how a paint mix ends up over-volume.

• Forgetting that a simplified ratio is not a smaller amount. 4:8 simplifies to 1:2 — same proportion, not half the recipe. If you actually want less, use Scale with a factor below 1, not Simplify.

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