You're right that I'm remembering my sig-fig rules wrong, but you're not entirely right: > Zeros to the right of the last non-zero digit (trailing zeros) in a

You're right that I'm remembering my sig-fig rules wrong, but you're not entirely right: > Zeros to the right of the last non-zero digit (trailing zeros) in a number with the decimal point are significant if they are within the measurement or reporting resolution. > 1.200 has four significant figures (1, 2, 0, and 0) if they are allowed by the measurement resolution. and > Trailing zeros in an integer may or may not be significant, depending on the measurement or reporting resolution. So my first example "1m and 1000mm" actually might be the same length, depending on if those zeros are significant or not which has not been clearly communicated. My second example "1000mm and 1.000m" is also ambiguous, since 1.000m is clear(ish) about its sig-figs, while 1000mm is not. I suppose I could have written "1000. mm" Best solution imo would probably be: - something that actually specified the error: 1m ± 0.0001m - or using words to indicate what's meant: "exactly 1000mm"