What this calculator does
Modular multiplicative inverse works out finds x such that a·x ≡ 1 (mod n), using the extended Euclidean algorithm. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
FormulaExists iff gcd(a,n)=1; found from a·x+n·y=1 via the extended Euclidean algorithm, then x mod n
The inputs explained
| Field | What to enter |
|---|---|
| a | A number. Starts at 7. |
| n (modulus) | A number. Starts at 26. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with a
Every other input is held at the calculator’s starting values while a varies. Select any row to load that scenario into the calculator.