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Reviewed by CalculatorApp.me Math Team
Add, subtract, multiply, divide fractions and mixed numbers with step-by-step solutions.
4 Ops
Add / Sub / Mul / Div
LCD
Least Common Denominator
GCD
Greatest Common Divisor
Mixed
Whole + Fraction
Free online fraction calculator — add, subtract, multiply, and divide fractions with auto-simplification and AI insights.
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A fraction represents a part of a whole. It is written as a/b where a (numerator) is the number of equal parts taken and b (denominator) is the total number of equal parts. For example, 3/4 means three parts out of four equal parts. Fractions are fundamental to mathematics, appearing in algebra, geometry, probability, and real-world applications from cooking to engineering.
Proper fractions have numerators smaller than denominators (3/4), improper fractions have numerators ≥ denominators (7/4), and mixed numbers combine whole numbers with fractions (1 3/4). Every rational number can be expressed as a fraction, making them one of the most versatile numeric representations.
The key challenge with fractions is finding common denominators for addition and subtraction & simplifying results using the GCD. This calculator automates both — providing step-by-step solutions with fully reduced answers.
a/b + c/d = (a×d + c×b) / (b×d) a/b − c/d = (a×d − c×b) / (b×d) Using LCD (more efficient): LCD = LCM(b, d) a/b + c/d = (a×(LCD/b) + c×(LCD/d))/LCD Example: 2/3 + 3/4 LCD = LCM(3,4) = 12 2/3 = 8/12 (2 × 4) 3/4 = 9/12 (3 × 3) 8/12 + 9/12 = 17/12 = 1 5/12 Always simplify the result using GCD(numerator, denominator).
Finding the LCD (Least Common Denominator) keeps numbers small. The cross-multiplication method always works but may produce larger intermediaries.
a/b × c/d = (a×c) / (b×d) Example: 2/3 × 5/7 = (2×5) / (3×7) = 10/21 (already simplified) Cross-cancel shortcut: 4/9 × 3/8 Cancel: 4↔8 (÷4), 3↔9 (÷3) = 1/3 × 1/2 = 1/6 Mixed numbers → improper first: 2 1/3 × 1 1/2 = 7/3 × 3/2 = 21/6 = 7/2 = 3 1/2
Cross-cancellation (dividing any numerator with any denominator by their common factor) simplifies before multiplying — keeping numbers manageable.
a/b ÷ c/d = a/b × d/c (flip & multiply) Example: 3/4 ÷ 2/5 = 3/4 × 5/2 = 15/8 = 1 7/8 Why flip & multiply works: (a/b) / (c/d) = (a/b) × (d/c) ← multiply by reciprocal Division by zero: a/b ÷ 0/d → UNDEFINED (division by zero is undefined)
Division by a fraction equals multiplication by its reciprocal. This is one of the most elegant identities in arithmetic.
| Fraction | Decimal | Percent | Simplified | Notes |
|---|---|---|---|---|
| 1/2 | 0.5 | 50% | 1/2 | Halves |
| 1/3 | 0.333… | 33.33…% | 1/3 | Repeating decimal |
| 2/4 | 0.5 | 50% | 1/2 | Simplifies by GCD=2 |
| 3/8 | 0.375 | 37.5% | 3/8 | Terminating decimal |
| 5/6 | 0.8333… | 83.33…% | 5/6 | Repeating |
| Fraction | ×2 | ×3 | ×4 | ×5 | LCD with 1/6 |
|---|---|---|---|---|---|
| 1/2 | 2/4 | 3/6 | 4/8 | 5/10 | 3/6 |
| 1/3 | 2/6 | 3/9 | 4/12 | 5/15 | 2/6 |
| 2/5 | 4/10 | 6/15 | 8/20 | 10/25 | 12/30 |
| 3/4 | 6/8 | 9/12 | 12/16 | 15/20 | 9/12 |
Ancient Egyptians used only unit fractions (1/n) plus 2/3. The Rhind Mathematical Papyrus contains tables converting fractions like 2/5 into sums of unit fractions: 2/5 = 1/3 + 1/15. This constraint made arithmetic complex but manageable on papyrus.
Babylonians used a sexagesimal (base-60) system still reflected in our 60 minutes/hour. Their positional notation allowed efficient fractional representation — 1/3 was exactly 20/60, avoiding repeating decimals entirely.
Book VII of Euclid's Elements describes the algorithm for finding the Greatest Common Divisor (now called the Euclidean Algorithm). This 2,300-year-old procedure remains the standard method for simplifying fractions and is still used in computer science.
Brahmagupta formalized rules for fraction arithmetic in Brāhmasphuṭasiddhānta, including operations with zero. Indian mathematicians wrote fractions vertically (numerator above denominator) without a bar — the bar was added by Arabic mathematicians later.
Siegler et al. (2013) — Psychological Science
A longitudinal study of 599 students found that 5th-grade fraction knowledge uniquely predicted algebra achievement in 10th grade, even controlling for IQ, reading ability, working memory, and whole-number knowledge. Fraction mastery is the strongest pre-algebra predictor.
NCTM — Principles and Standards
The National Council of Teachers of Mathematics emphasizes that fraction understanding requires visual models (area models, number lines, set models) before symbolic manipulation. Students who develop conceptual understanding outperform those taught procedures first.
National Mathematics Advisory Panel (2008)
The panel identified fractions as 'the most important foundational skill not possessed by students' and the single biggest barrier to algebra readiness. They recommended devoting major instructional time to fractions in grades 3-5.
Decimals are always better than fractions.
1/3 is exact; 0.333… is an infinite approximation. In algebra, probability, and pure mathematics, fractions preserve exactness. Decimals are better for measurement, money, and computation where fixed precision is acceptable.
You can add fractions by adding numerators and denominators.
1/2 + 1/3 ≠ 2/5. You must find a common denominator first: 1/2 + 1/3 = 3/6 + 2/6 = 5/6. The 'freshman sum' (a+c)/(b+d) is actually a mediant — useful in some contexts but NOT addition.
Multiplying fractions always makes them bigger.
Multiplying by a proper fraction (< 1) makes the result smaller: 1/2 × 1/3 = 1/6. Only multiplying by an improper fraction (≥ 1) or whole number increases the value.
Fractions are outdated — calculators replaced them.
Precision math tools for students, teachers, and professionals — CalculatorApp.me.
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To simplify a/b:
1. Find GCD(a, b)
2. Divide both: (a÷GCD) / (b÷GCD)
Euclidean Algorithm for GCD:
GCD(48, 18):
48 = 2×18 + 12
18 = 1×12 + 6
12 = 2×6 + 0
GCD = 6
48/18 = (48÷6)/(18÷6) = 8/3
To convert to mixed number:
8 ÷ 3 = 2 remainder 2
8/3 = 2 2/3
Fraction → Decimal:
a/b = a ÷ b
3/8 = 0.375
1/3 = 0.333... (repeating)The Euclidean Algorithm (c. 300 BC) is still the most efficient method for computing GCD — it runs in O(log(min(a,b))) time.
| 7/10 |
| 0.7 |
| 70% |
| 7/10 |
| Base-10 fraction |
| 15/25 | 0.6 | 60% | 3/5 | GCD=5 |
| 22/7 | 3.142857… | 314.28…% | 22/7 | π approximation |
Leonardo of Pisa (Fibonacci) introduced Hindu-Arabic fractions to Europe in Liber Abaci. He demonstrated that the Hindu-Arabic system made fraction arithmetic far easier than Roman numerals, catalyzing the adoption of modern fraction notation across European commerce and science.
Simon Stevin published 'De Thiende' (The Tenth), systematically introducing decimal fractions to Europe. This eventually led to the decimal point notation we use today, providing an alternative to common fractions for many practical calculations.
Knuth — The Art of Computer Programming
Knuth's analysis shows the Euclidean GCD algorithm (used for fraction simplification) runs in O(log φ × min(a,b)) time, where φ is the golden ratio. It has been the cornerstone of computational number theory since ancient Greece and remains optimal for its class.
Fractions are essential in algebra, calculus, and computer science. Programming uses integer ratios for exact arithmetic. Engineering tolerances, cooking recipes, music time signatures — all rely on fractional thinking. Understanding fractions is non-negotiable for math literacy.