Fraction Calculator

Add, subtract, multiply and divide fractions with automatic simplification

Calculate fraction operations with automatic simplification to lowest terms.

Updated June 2026 · How this works

Example calculation — edit any field to use your own numbers

Worth knowing
How It Works
The formula, explained simply

Think of fractions like slicing a pizza. When you add 1/4 + 1/8, you are combining a quarter-slice with an eighth-slice, but they are cut from different-sized pizzas. The calculator finds a common pizza size that both pieces can fit into, converts each piece to that size, then combines them.

The magic happens in finding the least common denominator. Instead of randomly picking a large number, the calculator finds the smallest number that both denominators divide into evenly. This keeps the numbers manageable and the result clean.

Simplification works by finding the largest number that divides evenly into both the numerator and denominator. If both can be divided by 6, the calculator does that division to give you the simplest form. This is why 6/8 becomes 3/4 automatically.

When To Use This
Right tool, right situation

Use this calculator when you need exact answers for measurements, recipes, or any situation where precision matters more than convenience. Fractions preserve exact ratios that decimals approximate, making them essential for carpentry, sewing, cooking, and mathematical work.

Fractions excel in situations involving division of whole quantities. If you are splitting profits among partners or dividing materials among projects, fraction results show exact proportions without rounding errors that compound over multiple calculations.

Avoid fractions when working with measurements that are already decimal-based, like metric units or currency. Also skip fractions for rough estimates where decimal approximations are sufficient, such as calculating tips or estimating travel times.

Common Mistakes
Why results sometimes look wrong

The biggest mistake is adding fractions by adding both numerators and denominators separately. This gives completely wrong answers because it ignores the fundamental meaning of fractions as ratios. Always find a common denominator first.

Another common error is forgetting to simplify results. While 10/20 and 1/2 are mathematically equivalent, the unsimplified version looks more complicated and can cause errors in subsequent calculations. Always reduce to lowest terms.

When working with mixed numbers, people often forget to convert them to improper fractions before calculating. You cannot multiply 2 1/3 × 1/4 directly - you must first convert 2 1/3 to 7/3, then multiply to get 7/12.

The Math
Worked examples and deeper derivation

Fraction arithmetic follows specific rules that preserve exact values. Addition and subtraction require a common denominator, found using the least common multiple of the original denominators. The formula for adding a/b + c/d becomes (ad + bc)/(bd), though the calculator optimizes by using the LCM instead of just multiplying denominators.

Multiplication is straightforward: multiply numerators together and denominators together. Division flips the second fraction and multiplies. The complexity comes in simplification, which uses the greatest common divisor to reduce fractions to lowest terms.

Mixed numbers appear when the numerator exceeds the denominator. The calculator extracts whole numbers by dividing the numerator by the denominator, keeping the remainder as the new numerator. This representation matches how people naturally think about quantities greater than one.

Recipe scaling
3/4 cup flour + 1/2 cup flour
When doubling a recipe that calls for 3/4 cup flour in one part and 1/2 cup in another, you get 1 1/4 cups total. This mixed number tells you exactly how much to measure without converting to decimals.
Construction measurements
7/8 inch bolt minus 1/4 inch for clearance
A 7/8 inch bolt with 1/4 inch clearance leaves 5/8 inch of engagement. Keeping the result as a fraction matches how construction measurements are marked on rulers and tape measures.
Investment portions
2/3 of portfolio times 3/4 allocation
If 2/3 of your portfolio is in stocks and you want to allocate 3/4 of that to domestic stocks, you get 1/2 of your total portfolio. The fraction shows the exact proportion without rounding errors.
Expert Unlock
The thing most explanations skip

Professional builders and machinists often work in fractions because their measuring tools are marked in fractional increments. A result of 15/32 inch can be measured directly on a fractional ruler, while the decimal equivalent 0.46875 requires conversion or interpolation.

How do I add fractions with different denominators?

How do you add fractions with different denominators?
Find the least common multiple of the denominators, convert both fractions to equivalent fractions with that common denominator, then add the numerators. For example, 1/4 + 1/6 becomes 3/12 + 2/12 = 5/12.
When should I use mixed numbers instead of improper fractions?
Mixed numbers like 2 1/3 are easier to visualize than improper fractions like 7/3, especially for measurements and real-world quantities. Use mixed numbers when the result represents something physical like cups, inches, or hours.
Why do my fraction results look different from decimal answers?
Fractions show exact values while decimals often round. 1/3 is exactly one-third, but 0.333 is an approximation. For precise work like carpentry or baking, fractions maintain accuracy that decimals lose through rounding.

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