---
title: "Significant Figures Calculator — Count & Round Sig Figs"
description: "Count significant figures in any number or round to n sig figs. Shows scientific notation and explains each rule. IB / AP / A-Level. Free sig figs calculator."
url: "https://worldcalculators.org/calculators/significant-figures/"
canonical: "https://worldcalculators.org/calculators/significant-figures/"
---

# Significant Figures Calculator

Count significant figures in any number or round to n sig figs. Shows scientific notation and explains each rule. IB / AP / A-Level. Free sig figs calculator.

## Quick answer

5 rules: (1) Non-zero digits are sig. (2) Sandwiched zeros are sig (1001→4). (3) Leading zeros never sig (0.042→2). (4) Trailing zeros with decimal are sig (3.20→3). (5) Trailing zeros without decimal are ambiguous.

## Frequently Asked Questions

0.00420 has 3 significant figures: 4, 2, and 0 (the trailing zero after 2 is significant because there is a decimal point). The leading zeros (0.00) are NOT significant — they only show the magnitude.
Ambiguous! Without a decimal point, trailing zeros may or may not be significant. To remove ambiguity, use scientific notation: 1.2 × 10³ (2 sig figs), 1.20 × 10³ (3 sig figs), 1.200 × 10³ (4 sig figs). A decimal point after 1200. (1200.) implies 4 sig figs.

Source: https://worldcalculators.org/calculators/significant-figures/
Markdown mirror of the HTML page. Prefer this URL for RAG; the interactive calculator still lives on the HTML page.