A.1.8—Order-of-magnitude calculations

An order of magnitude is a factor of ten. Rewrite values in standard form and compare the powers of ten before worrying about small coefficient differences.

For a quick estimate, round the coefficient to a convenient value, state the scale and then return to the exact calculation if the distinction matters.

A bacterium near 2 × 10⁻⁶ m and a cell near 2 × 10⁻⁵ m differ by one order of magnitude, even though both coefficients are 2.

A factor of two is not an order-of-magnitude difference; do not confuse percentage change with powers of ten.