Effective Tax Rate
Also called: average tax rate, overall tax rate
Your effective tax rate is total tax divided by total income — the average share you actually paid. It's always lower than your marginal rate under a progressive system, often dramatically: a US filer in the 24% bracket typically has an effective rate near 14%. Use effective rate to understand your burden and marginal rate to make decisions; confusing the two is how people conclude that earning more isn't worth it.
Formula
Effective tax rate = Total tax ÷ Total income