Ratio Calculator — Solve A/B = C/D (with visuals)

Enter any three values or pick a variable to solve. Private by design—everything runs locally in your browser.

Inputs & Actions

Solve for:

Visuals (A:B)

Pie

Left 3, Right 4

3
4

Width 4, Height 3

4 × 3

Aspect preview (width=B, height=A)

How This Tool Works

This ratio calculator helps you solve for a missing value in a ratio (A:B = C:D) and provides a visual representation of the ratio A:B. This is useful for scaling designs, recipes, or any other proportional relationships.

Ratio Calculation

The core formula used is `D = (B * C) / A`. The tool takes the three known values and automatically solves for the fourth, displaying the result in the disabled input field. All calculations are performed instantly in your browser.

Visual Representations

  • Pie Chart: The pie chart visually divides a whole into the two parts of the ratio (A and B).
  • Parts Bar: This bar shows the proportional relationship between A and B in a linear format.
  • Ratio Rectangle: A rectangle is drawn with its width and height proportional to the ratio A:B, helping you visualize aspect ratios.

Privacy Notice

This tool runs entirely in your web browser. No data is sent to a server, ensuring your calculations remain completely private.

Ratio Calculator: FAQs

How do I solve for the missing term in A:B = C:D?

If A, B, and C are known and A ≠ 0, then D = (B × C) / A. The calculator does this automatically.

What can I use ratio visuals for?

Scaling recipes or designs, understanding aspect ratios, comparing parts, and planning responsive layouts or print sizes.

Is my data private?

Yes. Everything runs client-side; nothing is uploaded.

5 Fun Facts about Ratios

Scaling leaves ratios intact

Multiply both sides by any nonzero constant and the ratio stays the same—why recipes work whether you cook for 2 or 200.

Proportion magic

Golden ratio everywhere

The famous φ ≈ 1.618 shows up in art, plants, and design grids. It’s the ratio whose reciprocal is just φ − 1.

Design darling

Aspect ratios are ratios, too

16:9 screens, 3:2 photos, or 4:3 classics—they’re all simple ratios of width to height shaping your canvas.

Screen DNA

Mixers love parts

Bartenders and chemists speak in “parts”: 2 parts tonic to 1 part syrup equals a 2:1 ratio no matter the glass size.

Parts language

Cross-multiply for checks

If A:B = C:D, then AD = BC. One quick product check spots typos and keeps proportions honest.

Sanity test

Explore more tools