Understanding Significant Figures
Significant figures (SF) are the digits in a measurement that can be counted on to be exact. Learning to identify them helps you express scientific measurements with the right precision.
There are three key rules to remember. First, non-zero numbers are always significant (for example, 3500 has 2 significant figures, and 50000 has just 1). Second, zeros between two significant digits count too - so 501 has 3 SF and 4303 has 4 SF.
The third rule involves decimals: trailing zeros after the decimal point are significant. This means 90.01 contains 4 SF, while 0.000050 has 2 SF (only the 5 and 0 after it).
⚠️ Important exception: Exact numbers (like unit conversions) have infinite significant figures. Examples include "12 inches = 1 foot" and "24 hours = 1 day" - these are 100% true by definition, so all digits count.
