Percent Error and Sig Figs
Percent error is a direct way to compare a measured value with an accepted value. It shows the size of the difference as a percent of the accepted value. This calculator keeps the sign when needed. It also shows the absolute percent error for reports that need only error size.
Why Significant Figures Matter
Significant figures control how much detail should appear in a final answer. A result with too many digits can look more exact than the experiment allows. A result with too few digits can hide useful precision. The sig fig setting lets you round percent error, absolute error, and relative error in a consistent way.
Advanced Statistical Checks
A tolerance limit helps decide whether a result is acceptable. The calculator compares the absolute percent error with your chosen tolerance. It can also use measured and accepted uncertainties. When both uncertainties are entered, the combined uncertainty is found with a root sum square method. This helps judge whether the difference is large relative to expected measurement spread.
Signed and Absolute Error
Signed percent error tells direction. A positive value means the measured value is above the accepted value. A negative value means it is below. Absolute percent error removes direction. Many lab reports use absolute percent error because they focus on accuracy rather than bias.
Better Lab Reporting
Good reporting should include the measured value, accepted value, units, percent error, rounding rule, and tolerance result. The example table shows how different trials can be organized. CSV export helps move results into spreadsheets. The PDF option gives a simple record for saving or printing.
Common Use Cases
This tool is useful for chemistry labs, physics measurements, quality checks, survey estimates, and statistical validation. It works with decimals, large values, and scientific notation. The accepted value cannot be zero when percent error is required, because division by zero is undefined.
Final Notes
Percent error does not explain why an error happened. It only measures the gap. Use it with notes about instruments, sampling, rounding, calibration, and procedure. A small percent error usually suggests strong agreement. A large value suggests possible bias, noise, or an incorrect reference. Always match precision to the weakest trusted measurement source.