Why your calculator is often wrong about the precision of your measurements
In short: Calculators provide raw numbers, but they ignore the reality of measurement uncertainty. This guide explains how to correctly round your results when adding or subtracting values, ensuring your final answer reflects the actual precision of your data.
Every measurement contains an estimated final digit, meaning your calculated result cannot be more precise than your least precise input. When performing addition or subtraction, the rule is to round your final answer to match the number of decimal places found in the measurement with the fewest decimal places.
To apply this, first calculate the unrounded sum or difference. Then, identify which of your original measurements has the fewest decimal places. Finally, round your calculator result to that specific decimal position to maintain scientific accuracy.
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Sources
- Summary by Intellect · source: Adding and subtracting significant figures | Science Toolkit | Khan Academy
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