What this site is
LCM Calculator is a small, static, browser-based tool for computing least common multiples and greatest common divisors, with additional modes for lowest common denominators, rational inputs and ranges. It is written for students and general users who want both an answer and a readable explanation of how that answer was obtained.
Every page is plain HTML with a shared stylesheet. The calculator runs entirely in the browser; there is no server-side computation, no account, and no database.
How the arithmetic is performed
- Exact integers. Integer values are handled as signed BigInt values. Inputs may be up to 100 digits long, and results are exact — there is no rounding or floating-point comparison anywhere in the integer path.
- Two to twenty entries (normal input). A normal multiple-entry calculation accepts between 2 and 20 integers, folded pairwise from the left. Range mode is separate: it takes a single value n from 2 to 100 and computes the LCM of 1 up to n, so the 2-to-20 rule does not apply there.
- Negative and zero handling. Negative inputs are reduced to their magnitude. If any input is zero the result is 0 by convention, and an all-zero GCD is reported as 0.
- Several honest methods. The site can show GCD/Euclid, prime powers, the ladder method, listing multiples, common division and binary GCD. Where a method cannot be completed within its limit, the working says so and falls back to Euclid rather than presenting a partial result as complete.
- Stated limits. Prime factorisation is restricted to inputs whose absolute value is 1,000,000 or less. Listing displays the first 12 multiples and searches internally within a 10,000-step budget. Range mode accepts n up to 100.
- Rational mode. Fractions written as a/b and finite decimals with up to 12 decimal places are accepted, reduced first, and combined using LCM of the reduced numerators over GCD of the reduced denominators. A separate LCD option works from the reduced denominators and outputs equivalent fractions.
- Batch mode. Up to 50 lines can be processed at once, each line containing 2 to 20 signed integers.
- No storage surprises. History is kept in page memory for the current session only. The optional "save history on this device" checkbox stores at most 8 entries in localStorage. The colour theme is also stored in localStorage. These are the calculator's own settings; separate Google Analytics and advertising behaviour is described on the privacy page.
How the site behaves
| Aspect | Behaviour |
|---|---|
| Offline use | Open index.html directly from the folder. No installation, no service worker and no download step are required. |
| Sharing | Sharing happens only when you explicitly choose it. On a hosted site, the link carries the calculation in the URL fragment. When opened as a local file, Share copies the solution text instead; Download separately saves a solution file. |
| Analytics and network requests | The calculator does not send your inputs anywhere. After you accept a cookie banner, the site loads Google Analytics 4 for aggregate traffic measurement (which sets _ga cookies) and a separate third-party advertising banner; both stay off if you decline. See the analytics and advertising privacy details. |
| Keyboard and assistive technology | The site aims at WCAG 2.2 AA; see the accessibility page for what is implemented and what has not been verified. |
What this site does not claim
- No named author, reviewer, credential or institutional affiliation is presented, because none is asserted here.
- No ratings, reviews, testimonials, rankings or awards are displayed, and none are solicited.
- No performance, ranking or indexing outcome is guaranteed. Search engines decide those; the privacy and terms pages set out the limits in more detail.
- No mathematics here is new. The methods are established number theory, applied in the browser; nothing is presented as a 2026 discovery.
- The calculator's arithmetic has no third-party runtime dependencies. The page does load two external services: Google Analytics 4 for aggregate traffic measurement, and a separate advertising banner above the footer. Source and social links also lead to external sites; their practices are outside this calculator's control.
Sources consulted
Search guidance was rechecked on ; the accessibility references below were reviewed on 18 September 2026. Older publication dates are not relabelled as new research. The mathematics remains established; these dates describe this site's review, not the invention of the methods.
Search and publishing guidance
- Google Search: AI optimization guide — used for the fundamentals position: ordinary, useful, well-structured pages are the point, and no special
llms.txtfile or special AI-only schema markup is required. - Google Search: updates — it records that the FAQ rich result feature was removed in May 2026, which is why these pages make no promises about FAQ rich results and carry no FAQPage markup.
- Google Search: core updates — treated as older guidance about how such updates generally work, not as a 2026 rulebook.
Performance and accessibility
- web.dev: Web Vitals — an ongoing living document whose original publication is older than the current revision. Used for the general vocabulary of Core Web Vitals; no field measurements for this site are claimed.
- W3C: Web Content Accessibility Guidelines 2.2 — an established W3C Recommendation, older than this site but directly relevant, and the standard the accessibility work aims at. The site has not been audited or certified against it.
Mathematics references
- MathWorld: Least Common Multiple — used for the standard definition and the LCM–GCD relationship. Established mathematics, not a recent invention.
- Mathematics Stack Exchange: GCD and LCM of fractions — a community discussion from 2011, used as supplementary context for the rational convention. It is not an official standard, and the rational mode is labelled as a convention on the How it works page for that reason.
- Yaffle/bigint-gcd — read as a research reference on approaches to large-integer GCD. The code is not bundled or copied: the Euclid and binary GCD implementations in this site are original.
- CalculatorSoup: LCM calculator — a competing page, consulted only to understand the general feature landscape of online LCM tools. No text, layout, wording or data was copied from it.
Following external links is a normal web activity: when you click one, your browser connects to that site and the usual network information (such as your IP address and browser details) is visible to it. Loading the separate advertisement also makes external requests, without clicking a source link. See the privacy page for the full picture.
Corrections and context
To check a result, compare the working with the method guide and try another method on the same inputs. Include the inputs, calculation mode, chosen method and expected result when reporting a discrepancy. You can report a calculation or site issue on GitHub. A GitHub account is required; reports are public, so omit personal or sensitive information. This is not a private support channel, and a response time is not guaranteed. Linked references remain the authority for their own content. See the terms of use.