Leading zeros never count. Zeros between digits count. Trailing zeros after a decimal count; in an integer they may be ambiguous.

This tool shows the count plus a short reminder of the rules so you can verify.

Same as significant-figures tool?

Same counting logic; this one emphasizes the rules and explanation.

Online Significant Figures Counter

Count significant figures in a number and see the rules: leading zeros, trailing zeros, and which digits count.

Number

What are the rules?: Leading zeros never count. Zeros between digits count. Trailing zeros after a decimal count; in an integer they may be ambiguous.
Why show rules?: This tool shows the count plus a short reminder of the rules so you can verify.
Same as significant-figures tool?: Same counting logic; this one emphasizes the rules and explanation.

Celsius to Fahrenheit Converter

Convert Celsius to Fahrenheit and Fahrenheit to Celsius instantly. Free temperature converter.

Tip Calculator

Calculate tip and split the bill. Enter bill amount, tip percentage, and number of people.

Roman Numeral Converter

Convert numbers to Roman numerals and Roman numerals to numbers. Supports 1–3999.

Combinations Calculator

Calculate C(n,r) — the number of ways to choose r items from n without order. Uses n!/(r!(n-r)!).

Combinations with Replacement Calculator

Calculate the number of ways to choose r items from n with repetition allowed. Formula: C(n+r-1, r).

Even Permutations Calculator

Count how many permutations of n objects are even (expressible as an even number of swaps). For n ≥ 2, equals n!/2.