4% to 5% Is +1 Point and +25% at the Same Time — the Percentage Trap Most Calculators Ship

An interest rate moving from 4% to 5% rose by 1 percentage point and by 25% relative — both true, measuring different things. This calculator puts pp and percent change side by side, and fixes three more errors most tools get wrong: a 50% drop needs a 100% gain to recover, 80 after 20% off comes from ÷0.8 = 100 not ×1.2 = 96, and markup 150% equals margin 60% on the same 60 of profit.