One tool that answers every percentage question you actually ask. The ChrysoKit Percentage Calculator has seven modes covering "X% of Y", "X is what % of Y", percent change, add/subtract a percentage, reverse a percentage and percent difference.
Why use it
Percent math is easy in principle and surprisingly easy to get wrong in practice. A mode-specific layout removes the ambiguity, pick the question, fill the two known values, read the answer.
How to use the Percentage Calculator
- Pick a mode tab: % of a number, X is what % of Y, % change, Add %, Subtract %, Reverse %, or % difference.
- Fill in the two known values.
- Read the answer with the calculation written out underneath.
- Switch modes and reuse the same numbers if needed.
Features worth knowing
Seven modes
Every common percentage question is one tab away. The labels are written in plain language so you do not need to remember the formula.
Reverse %
"After a 20% discount, the price is 80. What was the original?" Reverse mode answers this without you flipping the math by hand.
Negative changes
Percent change is direction-aware. Going from 100 to 80 is a 20% drop, not a 20% gain.
Pro tips
- For tip and tax math, the "Add %" mode is faster than computing the percentage and then adding it manually.
- Percent change is direction-aware. Going from 100 to 80 is a 20% drop, not a 20% gain.
- When two numbers feel close, run "% difference" before assuming they are interchangeable.
Privacy first. The Percentage Calculator runs entirely in your browser.
Save the Percentage Calculator. Pull it out every time the mental version starts to feel uncertain.
Open the tool: Percentage Calculator →
Percentages in the news: a reader's self-defence course
A week of headlines provides a complete syllabus in percentage misdirection, no malice required... the conventions of compression do the work.
"Crime up 50% in the district" passes through every editorial filter and remains uninterpretable without the base: four incidents rising to six is 50%, and so is four thousand rising to six thousand. Relative change without absolute numbers is the most common gap, and the reader's reflex question... 50% of what?... resolves or exposes it instantly.
"Unemployment fell from 10% to 8%" gets reported as both "down 2%" and "down 20%", and both are defensible: two percentage points, twenty percent relative. The phrases are not interchangeable, and noticing which one a piece chose (usually the more dramatic) is half the course.
Health reporting supplies the advanced module: "the treatment cuts risk by 40%" compresses away the baseline. A risk falling from 0.5% to 0.3% is a 40% relative reduction and a 0.2-point absolute one... the number patients actually need (how many must be treated for one to benefit) lives in the absolute figures, which is why serious medical reporting states both.
None of this requires distrust... only the habit of reconstructing the underlying numbers before reacting. A calculator and thirty seconds turn most percentage headlines back into the plain arithmetic they compressed.