"Interest rates rose from 5% to 10%." Did they rise by 5%, or by 100%? The answer is both — depending on whether you mean percentage points or percentage. Mixing these up is one of the most common — and most consequential — statistics mistakes, showing up everywhere from news headlines to sales reports.
The core distinction
A percentage point is the simple, literal difference between two percentages. A percentage change (or relative change) expresses that same difference as a proportion of the starting value.
| Change | In percentage points | As a percentage change |
|---|---|---|
| 5% → 10% | +5 percentage points | +100% (it doubled) |
| 40% → 50% | +10 percentage points | +25% |
| 80% → 90% | +10 percentage points | +12.5% |
Notice how the same 10-point jump (40%→50% vs 80%→90%) produces very different percentage changes — 25% versus 12.5% — because percentage change depends on the starting value, while percentage points don't.
Why this matters in practice
This distinction isn't academic pedantry — it changes what a number actually means:
- Interest rates and inflation — a central bank raising rates "from 2% to 3%" is a 1 percentage point increase, but a 50% relative increase in borrowing cost.
- Conversion rates — going from a 2% to a 4% website conversion rate is "+2 percentage points" but "+100%" more customers — a huge difference in how impressive it sounds.
- Election polling — a candidate's support moving from 45% to 48% is a 3 percentage point swing, not a "3% increase" (which would only be about 1.4 points).
- Tax rates — a marginal tax rate rising from 20% to 25% is a 5 percentage point increase, equivalent to a 25% larger tax bill on that bracket.
How to calculate each one
Percentage point difference is simple subtraction:
New% − Old% = percentage point change
Percentage change requires dividing by the starting value:
(New% − Old%) ÷ Old% × 100 = percentage change
For the 5% → 10% example: percentage point change = 10 − 5 = 5 points. Percentage change = (10 − 5) ÷ 5 × 100 = 100%.
How to talk about it correctly
When communicating a change yourself, be explicit: say "a 5 percentage point increase" rather than just "a 5% increase" whenever there's room for ambiguity — especially in finance, politics, or any context where the distinction changes the story.