Significant Figures Calculator
Type the number exactly as written (for example 0.00420) — it counts how many significant figures it has, and also shows the rounded form for any target sig figs. Zero rules are important, so the number is taken as text.
How to use
- Write the number exactly as it is written — trailing zeros are also counted when there is a decimal point.
- Optional: also enter how many sig figs to round to.
Rules: non-zero digits are always significant; zeros between two significant digits are significant; leading zeros are never significant; in a decimal number, trailing zeros are significant. Scientific notation also works (for example 4.20e3).
Frequently Asked Questions (FAQ)
Why do I type the number exactly as written?
Because trailing zeros matter: for example in 0.00420 the trailing zero counts when there is a decimal point, so the number is taken as text.
Can it round to a target?
Yes. Enter the number of significant figures you want and it also shows the rounded form.
What does the result show?
The count of significant figures in the number and the rounded result for any target sig figs you set.
Which significant figure rules does it use?
Non-zero digits are always significant, zeros between significant digits count, leading zeros never count, and trailing zeros count in a number with a decimal point.
Does it accept scientific notation?
Yes. Scientific notation like 4.20e3 works and is counted as written.