Percentage Error Calculator

Percentage error = |experimental - actual| / |actual| x 100%. It measures how far off a measured value is from the true value. A 2% error means your measurement was 2% away from the true value. Lower percentage error = more accurate measurement.

The absolute value |experimental - actual| gives us the magnitude of the error regardless of direction. Without it, being 5% too high and 5% too low would cancel out. Percentage error is always reported as a positive number representing the size of the discrepancy.

Depends on the field: Physics lab (student level): <5% is good, <10% acceptable. Analytical chemistry: <2%. Manufacturing quality control: often <1%. Medical devices: <0.5% or even less. Research science: depends on the measurement, but typically strive for <5%.

Percent error compares a measurement to a known true value: |measured - true| / |true| x 100%. Percent difference compares two measurements neither of which is designated the true value: |A - B| / ((A+B)/2) x 100%. Use percent error when a true value is known; percent difference when comparing two measurements.

Systematic errors (shift in one direction): calibrate equipment, use better measuring tools, control experimental conditions. Random errors (scatter in both directions): repeat measurements and average, use larger sample sizes. Human errors: double-check readings, use digital instruments, blind measurements.