The percent key on different calculators does different things — here's what to expect on phone, desktop, and four-function calculators.
Surprising but true: the percent key works differently on different calculators. Three main behaviors:
Most phone calculators and basic four-function calculators:
80 × 15 % = 12The % key divides the previous number by 100. So 15 % becomes 0.15, then multiplied by 80 = 12.
Some calculators interpret +% as “add this percentage”:
80 + 15 % = 92 (15% added)
80 − 15 % = 68 (15% subtracted)Useful for tax and discount calculations.
Scientific calculators (like iOS in landscape mode) often treat % as a postfix operator that simply means “÷ 100”:
15% = 0.15You then explicitly multiply: 0.15 × 80 = 12.
Standard mode does the Behavior 2 trick: 200 + 15% = gives 230. Scientific mode behaves differently.
Portrait orientation (basic): Behavior 2. 80 + 15% = gives 92.
Landscape orientation (scientific): Behavior 3. 15% gives 0.15.
Skip the % button. Convert manually: divide by 100 first, then multiply. 15 ÷ 100 × 80 always gives 12, on any calculator.
Because the calculator interprets +15% as "add 15% of the running value" (200 + 30 = 230). It is not adding 0.15. Different calculators handle this differently.
The four percentage formulas in Excel: percentage of a number, percentage change, percent of total, and formatting cells...
The same formulas work in Google Sheets as in Excel, with a few keyboard shortcut and formatting differences.
A worked example showing three ways to compute 15% of 80, with the mental-math shortcut that makes 15% of anything easy.