Multimeter Accuracy Calculator
Turn a multimeter's ±(% + digits) accuracy spec into an actual uncertainty range, and check whether your theoretical value falls inside it.
Reading the spec
Accuracy is usually listed as ±(0.8% + 3): 0.8% of the reading plus 3 counts of the last digit. One count (the resolution) is the range divided by the display counts, so the 20 kΩ range of a 2000-count meter resolves 10 Ω. Accuracy differs by function and range, so use the matching line in your meter's manual.
Frequently asked questions
What does ±(0.5% + 2) mean on a multimeter?
The error is 0.5% of the reading plus 2 counts of the last displayed digit. On a 2000-count meter's 20 V range the last digit is 0.01 V, so a 12.00 V reading is uncertain by 0.06 V + 0.02 V = ±0.08 V.
Why does the range setting matter?
The digit part of the error is a count of the last digit, and its size depends on the range. Measuring on the lowest range that still fits the value gives the finest resolution and the smallest error.