Free calculator
Significant figures calculator
Count significant figures (sig figs), round to a set number, or run + − × ÷ on two values with the usual homework rules: add/subtract to the fewest decimal places, multiply/divide to the fewest sig figs (round half up). E-notation like 1.23e-4 is fine. The Sheets/Excel block is a heuristic for rounding—spreadsheets do not count sig figs in a number cell the way a hand rule does (see methodology and FAQs).
When to use this tool
Quick homework and lab-prep checks: count sig figs from how you type a number, round, or combine two values under the usual first-course rules without fighting a hand calculator or spreadsheet for every line.
- Copy a measured value with E-notation and confirm how many significant figures the string implies.
- Round a messy intermediate to N s.f. to match a problem statement before you type the next line in Sheets or Excel for notes.
- Check + − × ÷ for two operands the way a textbook table describes—this page does not parse full PEMDAS lines with mixed operators in v1 (see FAQ).
We follow common first-course US-style rules. This page is not a lab measurement standard—instructors, disciplines, and jurisdictions can differ slightly on how edge cases (especially trailing zeros) are read when you did not use a decimal point in an integer that looks like a placeholder (for example, 100 on its own).
Counting
All nonzero digits are significant. Sandwiched zeros (between two nonzero digits) are significant. Leading zeros are not. Decimal present: trailing zeros to the right of the decimal are usually significant. No decimal in an integer: trailing zeros after the last nonzero are usually not (for example, 100 is often read as one); E-notation uses the mantissa to count, not the text of the exponent (the exponent is exact in order-of-magnitude).
Rounding to **N** significant figures (half up)
The tool rounds half up to N places (in the first N digits in scientific-style magnitude). Ties (exactly 0.5) go up; negatives round away from zero, consistent with a simple half-up for magnitudes. Displayed results may use E-notation so the N s.f. is visible when a plain decimal would be ambiguous (for example 1.0e+1 for the number 10 to 2 s.f.).
Addition and subtraction (decimal places)
The result of + or − is only as precise in the decimal direction as the weaker operand. When you type a plain decimal, we use the text to count digits after the .. For E-notation inputs, we count decimal places in the same value the token parses to (so 1.2e+2 behaves like 120 in plain form, 0 d.p. in that example), and if one operand is 0, the other’s precision limits the result.
Multiplication and division (sig figs)
The result of × and ÷ is rounded to the smaller of the two sig-fig counts, determined from each operand’s string with the same counting rules as the Count mode.
Multi-step expressions with different operators in one line are v1 out of scope—this tool runs one + / − / × / ÷ on a and b; chain steps by hand or in a spreadsheet if the assignment needs full order-of-operations. See the least to greatest calculator to sort a simple list, and the standard deviation calculator to describe spread from a pasted set.
For a pasted list, spread is on the standard deviation calculator page. To sort numbers before a summary, use the least to greatest calculator.
FAQs cover 100 vs 100.00, 0, Sheets/Excel limits, and why a displayed cell may differ from a strict sig-fig read.
Google Sheets and Excel (rounding heuristics)
A plain number cell in Sheets or Excel does not store a sig-fig flag; the program shows a displayed value. The usual workaround is: decide N, then use ROUND to a number of decimal places, or a ROUND-with-LOG10-style offset if you are forcing N s.f. in scientific notation. Replace the cell with your value.
=IF(A1=0,0,ROUND(A1*10^-(INT(LOG10(ABS(A1)))+1-N),INT(LOG10(ABS(A1)))+1-N))This is a single-cell illustration; N in 4 and 3 in the INT tail must match. Test your numbers—extreme magnitudes, negatives, and zero need a different case split than this one line.
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Frequently asked questions
How many significant figures are in 100 and 100.0?
Under common first-course integer reading, 100 (no decimal shown) is often treated as one s.f. because the trailing zeros are ambiguous placeholders. 100.0 (with a decimal) is usually read as four s.f.—the decimal marks that the last zero is a measured place. In E-notation like 1.0e+2 you can state two s.f. in the mantissa and treat the exponent as exact.
Is rounding “half to even” or “half up”?
This tool uses round half up to .5 (or half away from zero in magnitude for negatives). A few hand rules use round half to even (banker’s), and some teachers prefer that—if your class specifies it, re-check a borderline on paper.
Is this the same as “significant” in *financial* statements?
No. The phrase *significant figures* here means precision in measured numbers (chemistry, physics, general science homework). *Materiality* or *significance* in finance is a different business and accounting idea, even though the word is similar in English—use a planning or audit workflow if that is the problem you have.
Is there a Google Sheets function that *counts* sig figs in a value?
No built-in =SIGFIGS(…) exists. The usual approaches are: (1) store the value as a string in one cell and parse it with a formula; (2) teach ROUND-plus-LOG10 patterns for a fixed N s.f. for positive numbers (see the spreadsheet block); (3) re-type the value with a clear . to show that trailing 0s count when that is the rule. Our tool is a laboratory-style read of what you type; Sheets/Excel display formatting can otherwise hide the idea you are testing.
What about Excel 365 with a German or French language pack for ROUND and LOG?
Function names and argument order are localised. Use Formulas → Insert function and pick ROUND / LOG / ABS in your build; align parentheses with the help card for your language—INT in English may be Ganzzahl in German or ENT in French depending on version, so the exact sheet line may differ; keep A1 as a named cell in your file.
Can I type a full expression with parentheses like (a+b)*c in v1?
Not on this version. The Calculate tab is one + − × or ÷ on a and b. If your assignment is multi-step, compute intermediates one at a time, or use a spreadsheet to carry cells; a single-line PEMDAS form may ship in a future version if the team adds it for parity with the largest free tools.
Can I use this to certify a lab measurement or ISO tolerance table?
No. This page is a teaching and homework helper, not a GUM uncertainty engine, and not an international standards interpretation for traceability or calibrations—ask your lab QA and follow your SOPs and ISO documents when compliance matters.
Is 10XSheets giving me academic or course credit advice?
No. Grading rubrics (partial credit, significant-figure penalty rules) are between you and your school—this tool is an independent arithmetic check, not a substitute for a manual or instructor decision.