What is it?
The LCM and HCF Calculator finds the LCM (lowest common multiple) and the HCF (highest common factor, also called GCD) of two or more whole numbers.
Who is it for?
School students, teachers, and anyone solving sharing, scheduling or fraction problems.
How to use it
Type the Numbers, separated by spaces or commas. The answer appears as you type; there is no Calculate button. Tap Copy result to copy it, or Share on WhatsApp to send it.
When to use which
- HCF: the biggest equal pieces. Cutting ribbons of 24 cm and 36 cm into equal pieces with none left: HCF = 12 cm.
- LCM: when things line up again. Buses every 12 and 18 minutes leave together again after 36 minutes.
- Adding fractions: the LCM of the denominators is the lowest common denominator.
Checks
- For two numbers, HCF × LCM = the two numbers multiplied: 12 × 36 = 24 × 18 = 432.
- Numbers with HCF 1 are “co-prime”; their LCM is their product.
Only whole numbers work. For decimals, multiply all by 10 or 100 first, then divide the answer back.
Worked example
12, 18 and 30: HCF 6, LCM 180. So three bells ringing every 12, 18 and 30 minutes ring together every 3 hours, and 12, 18 and 30 metres of rope cut into equal pieces without waste gives pieces of 6 m.
Errors and how to fix them
- “Enter two or more whole numbers”: no decimals or a single number.
Open the tool: LCM and HCF Calculator
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Questions, or an error not listed here?
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