Everyday Math calculators, in short
These are the calculations people do wrong in their heads most often, usually because percentages get added instead of applied one after another. Each tool shows the arithmetic so you can check it.
Popular tools in this category
- Percentage Calculator — What is X% of Y, X is what percent of Y, and percentage increase or decrease between two numbers.
- Percentage Change Calculator — Percent increase or decrease from an old value to a new one, with zero-start and negative-value handling.
- Percentage Difference Calculator — Symmetric percent difference between two values, shown next to percent change in both directions.
What can you calculate here?
- What is X% of Y, X as a percent of Y, and percentage change between two numbers
- A monthly budget split into needs, wants, and savings, against what you really spend
- Which package size is cheaper once both are priced per unit
- A sale price from one or two stacked discounts, plus the effective discount
- Sales tax added to a price, or backed out of a tax-inclusive total
- A tip on the full check or pre-tax, split between any number of people
Which calculator do you need?
- If you're trying to find X% of a number or what percent one number is of another, use the Percentage Calculator.
- If you're trying to measure a percent increase or decrease, use the Percentage Change Calculator.
- If you're trying to add or subtract a percentage, use the Add or Subtract Percentage Calculator.
- If you're trying to turn a fraction or score into a percent, use the Fraction to Percent Calculator.
- If you're trying to work out a sale price, use the Discount Calculator.
Tools by task
Most used: Percentage Calculator · Discount Calculator · Percentage Change Calculator
Percentages
- Percentage Calculator — What is X% of Y, X is what percent of Y, and percentage increase or decrease between two numbers.
- Percentage Change Calculator — Percent increase or decrease from an old value to a new one, with zero-start and negative-value handling.
- Percentage Difference Calculator — Symmetric percent difference between two values, shown next to percent change in both directions.
- Add or Subtract Percentage Calculator — Add or subtract a percentage from any number, with the amount and the reverse.
- Fraction to Percent Calculator — Turn any fraction into a percent and decimal, with the simplified fraction.
Shopping and prices
- Discount Calculator — Sale price and savings from one or two discounts, with optional sales tax on the discounted price.
- Sales Tax Calculator — Add sales tax to a subtotal, or reverse it out of a total that already includes tax.
- Tip Calculator — Tip amount, bill total, and the split per person — with an option to tip pre-tax.
Start here
The decision tools and guides for everyday math
These go beyond a single figure: they solve backwards from what you can afford, compare scenarios, and name the input deciding the answer. The guides work the same questions through with real numbers.
Guides
- Percentage change vs percentage points — The difference between a 5-point move and a 25% move, with worked examples and the formulas behind both.
10 calculators
Percentages
Purpose-built tools for this task.
Everyday
Percentage Calculator
What is X% of Y, X is what percent of Y, and percentage increase or decrease between two numbers.
Everyday
Percentage Change Calculator
Percent increase or decrease from an old value to a new one, with zero-start and negative-value handling.
Everyday
Percentage Difference Calculator
Symmetric percent difference between two values, shown next to percent change in both directions.
Everyday
Fraction to Percent Calculator
Turn any fraction into a percent and decimal, with the simplified fraction.
Everyday
Add or Subtract Percentage Calculator
Add or subtract a percentage from any number, with the amount and the reverse.
Household Budgeting
Purpose-built tools for this task.
Everyday
Budget Allocation Calculator
Needs, wants, and savings dollar targets from take-home pay, using a standard split or your own percentages.
Everyday
Unit Price Comparison Calculator
Which of two or three products is the better deal, once price and package size are normalized to the same unit.
Discounts & Everyday Math
Purpose-built tools for this task.
Everyday
Discount Calculator
Sale price and savings from one or two discounts, with optional sales tax on the discounted price.
Everyday
Sales Tax Calculator
Add sales tax to a subtotal, or reverse it out of a total that already includes tax.
Everyday
Tip Calculator
Tip amount, bill total, and the split per person — with an option to tip pre-tax.
Every everyday math calculator
Each tool below shows the formula it uses, a worked example, and what the result means in practice.
- Percentage CalculatorWhat is X% of Y, X is what percent of Y, and percentage increase or decrease between two numbers.
- Percentage Change CalculatorPercent increase or decrease from an old value to a new one, with zero-start and negative-value handling.
- Percentage Difference CalculatorSymmetric percent difference between two values, shown next to percent change in both directions.
- Budget Allocation CalculatorNeeds, wants, and savings dollar targets from take-home pay, using a standard split or your own percentages.
- Unit Price Comparison CalculatorWhich of two or three products is the better deal, once price and package size are normalized to the same unit.
- Discount CalculatorSale price and savings from one or two discounts, with optional sales tax on the discounted price.
- Sales Tax CalculatorAdd sales tax to a subtotal, or reverse it out of a total that already includes tax.
- Tip CalculatorTip amount, bill total, and the split per person — with an option to tip pre-tax.
- Fraction to Percent CalculatorTurn any fraction into a percent and decimal, with the simplified fraction.
- Add or Subtract Percentage CalculatorAdd or subtract a percentage from any number, with the amount and the reverse.
Common questions about everyday math calculations
- Which percentage calculation do I need?
- Scaling a number calls for "what is X% of Y"; comparing a part to a whole calls for "X is what percent of Y"; measuring movement between two values is percentage change. The Percentage Calculator handles all three, with the arithmetic shown.
- Do stacked discounts add together?
- No. A 20% discount followed by a 10% discount is a 28% total reduction, not 30%, because the second is taken off the already-reduced price. The Discount Calculator shows the effective single discount.
- Should I tip on the pre-tax or post-tax total?
- Either is common; the Tip Calculator lets you choose. Tipping on the pre-tax subtotal is the stricter reading, and the difference on a normal check is usually small.
- How do I compare two package sizes fairly?
- Convert both to the same base unit and compare price per unit. The Unit Price Comparison Calculator does that within a measurement family and tells you how much cheaper the winner is.
- What budget split should I use?
- 50/30/20 is the common starting point, but the useful step is comparing a plan against what you actually spend. The Budget Allocation Calculator shows targets and the gap in dollars.