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Ratio Calculator

Solve missing ratio values, simplify ratios to their lowest terms, scale aspect ratios like 16:9, or split an amount by ratio.

Form: A : B = C : X
15.00

Standard Aspect Ratios & Resolutions

16:9 Widescreen 1920×1080 (FHD), 2560×1440 (2K QHD)
4:3 Standard 1024×768, Photo prints, iPad displays
21:9 Ultrawide 3440×1440 Cinematic & Gaming Monitors
1:1 Square 1080×1080 Instagram Posts & Avatars

Calculated Solution

Proportion Answer X = 15.00
Visual Distribution

Ratio Formulas Cheat Sheet

Proportion X = (B × C) / A
Simplification Term / GCD(A, B, C)
Aspect Height H₂ = W₂ × (H₁ / W₁)
Part Share Total × (Part / ∑Parts)
Comprehensive Educational Guide

Mastering Ratios, Proportions & Scale Factors

Learn how ratios express relationships between quantities, how to solve proportions using cross-multiplication, and how to scale image resolutions or recipes accurately.

1

What is a Ratio?

A ratio compares the relative sizes of two or more numerical values. Expressed as A:B, A/B, or "A to B", it indicates how many times one number contains another.

2

What is a Proportion?

A proportion is a statement that two ratios are equal (A:B = C:D). When three values are known, the unknown target X is calculated via cross-multiplication.

3

Simplification & GCD

Ratios are simplified by dividing all numbers by their Greatest Common Divisor (GCD). For example, 12:18:24 reduces to 2:3:4 when divided by 6.

Step-by-Step Practical Calculations

Example 1: Solving 2:3 = 10:X

Goal: Find unknown value X in equivalent ratio.

  1. Write as equivalent fractions: 2 / 3 = 10 / X
  2. Cross-multiply: 2 × X = 3 × 10 = 30
  3. Solve for X: X = 30 / 2 = 15
Example 2: Dividing $1,000 in Ratio 2:3:5

Goal: Share a total amount proportionally.

  1. Sum all ratio parts: 2 + 3 + 5 = 10 total parts
  2. Value of 1 part: $1,000 / 10 = $100 per part
  3. Share 1: 2 × $100 = $200, Share 2: 3 × $100 = $300, Share 3: 5 × $100 = $500

Real-World Practical Applications

🍳

Culinary & Baking

Scale recipe ingredient quantities accurately when increasing or decreasing serving sizes without altering flavor profiles.

📐

Architecture & Maps

Convert blueprint scale dimensions (e.g. 1:50 or 1:100 scale) into actual real-world meters or feet accurately.

🖥️

Digital Video & Display

Maintain 16:9, 4:3, or 21:9 image and video aspect ratios to avoid stretching or letterboxing distortion.

📈

Business Finance

Analyze financial leverage ratios like Debt-to-Equity (D/E), profit sharing ratios, and investment portfolio splits.

Formula Reference

Ratio & Proportion Formula

Ratio and proportion formulas divide a total quantity into proportional parts based on specified ratio terms or test equality between two fractions (a/b = c/d).

$$\text{Share}_A = \text{Total} \times \left(\frac{A}{A + B + C}\right)$$
View Full Formula, Step-by-Step Guide & Worked Examples
Mathematics

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How Ratio Calculations Work

01

Solving a Ratio Proportion

A proportion A:B = C:X is solved by cross-multiplication: A x X = B x C, so X = (B x C) / A. For example, in 2:3 = 10:X, X = (3 x 10) / 2 = 15.

02

Simplifying a Ratio with the GCD

A ratio is simplified to its lowest terms by dividing every term by their greatest common divisor (GCD). The ratio 4:6 has a GCD of 2, so it simplifies to 2:3, and this same GCD method extends to three-term ratios such as 4:6:8, which simplifies to 2:3:4.

03

Dividing an Amount by a Ratio

To split a total amount by a ratio such as 2:3:5, add the parts together (2 + 3 + 5 = 10 parts) and divide the total by that sum to find the value of one part. For a total of 1,000 split 2:3:5, one part equals 100, giving shares of 200, 300, and 500.

04

When to Use Related Math Tools

Use the Fraction Calculator when a ratio needs to be added to or compared against a fraction, and the LCM & HCF Calculator when you need the underlying common divisor or multiple used to simplify or scale a ratio.

Good to know

Questions, answered

Quick answers about how this tool works.

Use cross-multiplication: A × X = B × C, so X = (B × C) ÷ A. For example, in 2:3 = 10:X, X = (3 × 10) ÷ 2 = 15.

Add the ratio parts (2 + 3 + 5 = 10 parts). Divide the total amount by 10 to find 1 part value, then multiply each ratio number by the 1 part value.

A ratio compares the relative sizes of two or more values. To simplify a ratio, divide all numbers by their greatest common divisor (GCD). For example, 15:20 simplifies to 3:4.

Sum the parts of the ratio to get the total parts. Divide the number by the total parts to find the value of one part, then multiply by each ratio term.

The golden ratio is a special mathematical ratio of approximately 1:1.618 (phi), widely used in art, architecture, and design for aesthetic proportions.

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