Everyday Money Math Calculators
Quick answers to the money math that comes up every day: what a percentage works out to, how much a discount saves, what to tip and how to split it, and how to price something for a profit.
3 calculators · 3 guides
Profit Margin Calculator
Calculate profit margin and markup from cost and price, or find the selling price for a target margin or markup — with a margin-to-markup conversion table.
Percentage Calculator
Four quick percentage calculators: what is X% of Y, X is what percent of Y, percent change between two numbers, and percent off a price.
Tip Calculator
Calculate the tip and total for any bill at 15%, 18%, 20% or a custom percentage, tip on the pre-tax amount, and split the check — with optional rounding.
Percentages are behind almost every money decision
Sales tax, discounts, raises, interest rates, and investment returns are all percentages, and most mistakes come from mixing up what the percentage is “of.” A 25% discount followed by another 10% off is not 35% off; it’s 32.5%, because the second discount applies to the already-reduced price. Writing out the base each time keeps the math honest.
Percent change works the same way. A price that rises from $50 to $65 went up 30%, but falling back from $65 to $50 is only a 23% drop, because the starting point changed. The percentage calculator handles each of these questions separately so the base is always clear.
Margin and markup are not the same number
If something costs you $40 and you sell it for $60, your $20 profit is a 50% markup on cost but a 33% margin on the price. Businesses that confuse the two underprice their products: aiming for a 50% margin by adding 50% to cost leaves them at 33%.
The profit margin calculator converts between the two and works backward from a target margin to the price you need to charge, with a table of common margins and their equivalent markups.
Guides & articles
Plain-English explainers to go with the calculators above — every figure tied to its source.
How Much to Tip: A Guide for Every Situation
Tipping norms have drifted, and the screen at the counter doesn’t help. Here are the common U.S. ranges for every situation, whether to tip on tax, and the mental math to get it right in seconds.
Markup vs. Margin: Formulas and Conversion Table
A 50% markup is only a 33% margin. Mixing the two up is one of the most common pricing mistakes — here are both formulas, a conversion table, and how to set a price that hits your target.
How to Calculate a Percentage (4 Formulas)
Almost every percentage question is one of four formulas. Here they are with worked examples — plus the mental-math tricks for tips and sale prices, and the one mistake that trips up percent change.