Percentage formatting displays 0.15 as 15%. If the source already contains 15 to mean fifteen percent, applying Percentage can produce 1500% instead.
Inspect the stored scale
Select a sample cell and inspect its value using a neutral numeric display. Establish whether the source represents proportions as 0.15, percentages as 15, or text such as 15%.
Compare several known records rather than deciding from one value. A mixed-source column may contain more than one representation, so dividing the entire column by 100 can corrupt entries that were already proportions.
Normalize with an explicit rule
For verified percentage-point inputs, a helper calculation =A2/100 converts 15 to 0.15. Apply Percentage formatting to that result. Keep the original until the scale has been reconciled.
For recognized percentage text, test VALUE against the file’s locale and compare the resulting fraction. Do not remove the percent sign and assume the remaining digits automatically have the correct scale.
Check formulas and reports
Test zero, fifteen percent, one hundred percent, and any legitimate negative or above-one-hundred values. The business context determines which values are valid; a large percentage is not always an error.
Inspect formulas that consume the column so conversion is not applied twice. For rates, verify the numerator and denominator as well as the display. Label whether a reported change is a percentage-point difference or a relative percentage change. A correct number format cannot resolve an ambiguous source scale, so retain uncertain records for review rather than forcing every value into an expected visual range.
References
Reviewed against the linked official product guidance on November 3, 2026. Features, limits, screen labels, and access can vary by account, platform, region, and organization policy.