---
title: "How to Calculate with Fractions and Decimals — Add, Subtract, Multiply, Divide, Convert"
description: "Learn to add, subtract, multiply, and divide fractions step by step. Convert between fractions and decimals. How decimal notation differs between countries (comma vs period)."
url: "https://worldcalculators.org/learning/how-to/fractions-decimals/"
canonical: "https://worldcalculators.org/learning/how-to/fractions-decimals/"
---

# Fractions & Decimals

Learn to add, subtract, multiply, and divide fractions step by step. Convert between fractions and decimals. How decimal notation differs between countries (comma vs period).

## Quick answer

Adding fractions: find common denominator → add numerators. ½ + ⅓ = 3/6 + 2/6 = 5/6. Multiplying: multiply straight across. ½ × ¾ = 3/8. Dividing: flip the second fraction and multiply. ½ ÷ ¼ = ½ × 4/1 = 2. Fraction to decimal: numerator ÷ denominator. ¾ = 0.75.

## Step-by-Step: Adding Fractions with Different Denominators

Find the lowest common multiple (LCM) of the two denominators. For 1/3 + 1/4, the LCM of 3 and 4 is 12.
Rewrite each fraction over the common denominator. 1/3 = 4/12 and 1/4 = 3/12.

## The Four Operations

Find common denominator, subtract numerators
Multiply numerator × numerator, denominator × denominator

## Converting Between Fractions and Decimals

Count decimal places. Write as that power of 10, then simplify.

## Decimal Notation Around the World

The decimal point is not universal — it is a cultural convention:
This is the most common source of international calculation errors — a price of "1.500" means $1,500 in Germany but $1.50 in the US.

Source: https://worldcalculators.org/learning/how-to/fractions-decimals/
Markdown mirror of the HTML page. Prefer this URL for RAG; the interactive calculator still lives on the HTML page.