Question 1

How do you count significant figures?

Accepted Answer

Start at the first non-zero digit and count every digit from there, including zeros between digits and zeros after the decimal point; skip only the leading zeros. 0.004520 has four; 100.0 has four; 100 has one, two or three, which is why scientists write 1.00 × 10² when they mean three.

Question 2

How many sig figs are in 0.05, 100 and 1.50?

Accepted Answer

0.05 has one: the zeros only place the 5. 100 is ambiguous and is usually read as one. 1.50 has three — the trailing zero after the decimal point was written on purpose. Paste any of them into the calculator to see the count and the reason for it.

Question 3

Do trailing zeros count?

Accepted Answer

After a decimal point, yes: 1.50 has three. In a whole number like 1200 there is no single answer, which is why science writes 1.2 × 10³ or 1.200 × 10³ instead.

Question 4

How many figures should a result keep?

Accepted Answer

As many as the least precise input. 2.5 times 3.42 gives 8.55, but it should be written 8.6 — two figures, matching the 2.5.

Question 5

How is this different from decimal places?

Accepted Answer

Significant figures count from the first non-zero digit; decimal places count from the point. 0.004520 has four significant figures and six decimal places.

Question 6

Why use scientific notation?

Accepted Answer

It states the number of significant figures unambiguously and handles very large and very small numbers cleanly.

Significant Figures Calculator

Result

Related tools

Rounding Calculator

Scientific Notation Converter

Standard Deviation Calculator

Useful links