Math & Scientific
GCF Calculator
GCF: GCF Calculator uses integer factorisation and the Euclidean algorithm to find the result exactly. Worked through below with real figures, and the calculator repeats the working on your own inputs — free, on-device, instant.
GCF Calculator is a browser-based way to work through a calculation. Feed it your numbers and it computes the result on the spot, keeping your data local.
About this calculator
GCF is easiest to get wrong in the setup, not the arithmetic. GCF Calculator uses integer factorisation and the Euclidean algorithm to find the result exactly. It matters when you need the exact relationship checked quickly rather than worked through by hand. The worked example on this page (GCF of 12 and 18: shared factors give 2 × 3 = 6 (12 = 2²×3, 18 = 2×3²).) shows the full substitution; the calculator above runs the same working on your own numbers, in your browser, with nothing uploaded.
How to use
- Enter two or more whole numbers, e.g. 12, 18, 24.
- Press Calculate to run the gcf calculator.
- Read the result: the greatest common factor, with the LCM shown alongside.
- Press Reset to clear the gcf calculator and start again.
Why use GCF Calculator
Fast
Calculations run in your browser. No round trip to a server.
Private
Your inputs never leave your device. Nothing is uploaded.
Free
No signup, no paywall, no ads-in-results, no watermarks.
Accurate
Based on standard, well-established formulas.
Mobile-ready
Optimised for phones, tablets, and desktops alike.
Transparent
Honest disclaimers wherever browser limits or regional rules apply.
Common uses
Use it when revising for exams
Use it when comparing two different methods
Use it for verifying answers from a textbook
Use it for homework and assignment checks
Use it for science-fair and project numbers
GCF in competitive-exam practice
Technical notes
GCF Calculator uses integer factorisation and the Euclidean algorithm to find the result exactly.
Zero values are retained: GCF(0, a) is |a|, and LCM is 0 if any input is 0. For an all-zero list both displayed results are 0 by convention. Inputs are taken exactly as entered, so check for typos before trusting an answer.
Nothing you type is uploaded — the calculation happens entirely on your device.
FAQ
What is the greatest common factor?
The largest whole number that divides all of your numbers exactly.
How many numbers can I enter?
Two or more — separate them with commas or spaces, e.g. 12, 18, 24.
Does it also give the LCM?
Yes, it returns both the GCF and the least common multiple of the same numbers.
Does the GCF Calculator send my data to a server?
No — the GCF Calculator runs entirely in your browser, so the numbers you enter never leave your device.
Worked example
GCF of 12 and 18: shared factors give 2 × 3 = 6 (12 = 2²×3, 18 = 2×3²).