Significant figures can look like a small classroom rule until you are doing lab work, chemistry, physics, or any kind of measurement-based calculation. Then the real question becomes practical very quickly: how many digits should this value keep, and how should the result be reported after arithmetic?
This page matches those two needs directly. In count mode, it helps you decide how many significant figures a number contains. In operation mode, it performs arithmetic and applies the page's classroom-style precision rules, while also explaining why the result was kept at that precision. That explanation is what makes the tool especially useful for learning.
The page offers count and operation mode. The first is for the question, "How many significant figures are in this number?" The second is for the question, "After I do the math, how should I report the result?"
Count mode needs one value. Operation mode needs two. The page accepts ordinary number formats and can also interpret the coefficient part of scientific notation.
The current page supports count mode and operation mode for sig-fig counting and precision-handled arithmetic.
Yes. The page reads the coefficient part of scientific notation when counting significant figures.
No. Multiplication and division use the smaller sig-fig count, while addition and subtraction use the smaller number of decimal places.
Not always. In addition and subtraction cases it behaves more like a precision-control cue, so it should be read together with the explanation text.
Calculate the number of significant figures in a number and perform operations following significant figure rules