How many significant figures?
Enter a number (e.g., 0.00340, 1200, 1.2300e3). We’ll count sig figs, highlight significant digits, and explain the rules used.
Results
About this Significant Figures Calculator
This tool helps you quickly determine the number of significant figures (sig figs) in any number, including decimals, whole numbers, and scientific notation. It not only counts sig figs, but also highlights significant digits and explains which rules apply, so you can understand why the count is correct.
How it works
- Enter a number (e.g.,
0.00340,1200,1.2300e3). - The calculator parses your input and applies the standard sig fig rules.
- Significant digits are highlighted and a rule‑by‑rule explanation is provided.
- You can control whether trailing zeros in integers are counted as significant.
Examples
0.0045→ 2 sig figs (digits 4 and 5; leading zeros not significant).2.300→ 4 sig figs (trailing zeros after decimal are significant).1002→ 4 sig figs (zeros between 1 and 2 are significant).1200→ ambiguous (2 sig figs if trailing zeros not counted; 4 if counted).1.2300 × 10³→ 5 sig figs (exponent doesn’t affect the count).
FAQ
What digits are significant?
All non‑zero digits are significant. Captive zeros (between non‑zeros) are significant. Leading zeros are not. Trailing zeros are significant only with a decimal point (or in scientific notation).
Are trailing zeros in integers significant?
They are ambiguous. The calculator lets you choose whether to treat them as significant or not. For clarity in real work, prefer scientific notation.
Does scientific notation affect the count?
No — the exponent is ignored for counting. Only the coefficient (mantissa) determines the number of significant figures.
Why are significant figures important?
They communicate the precision of a measurement or calculation and help avoid overstating certainty in scientific or engineering contexts.
Methodology & limitations
- Implements common rules used in science/engineering for decimals, integers, and scientific notation.
- Integers without a decimal point can be ambiguous if they end in zeros — use scientific notation to state intent.
- Input parser accepts signs (+/‑), decimals, and
e/Enotation (e.g.,1.23e4).