Everyday Math Calculators
Percentages, proportions, tips, discounts, fractions, and ratio conversions with instant clarity.
- Percentage Calculator: Quickly solve any percentage question: find what percentage a number is, calculate percent of a total, or measure percent increase and decrease.
- Proportion Calculator: Solve for any missing term in a ratio or proportion (A : B = C : D) with instant cross-multiplication steps and scale factors.
- Discount Calculator: Quickly find your final price and total dollar savings on any item on sale, with support for stacked coupons and local sales tax.
- Tip Calculator: Easily calculate tips for restaurants, delivery, and services. Split checks accurately between any number of guests with optional dollar rounding.
Frequently asked questions
How do I quickly calculate a percentage discount in my head?
To calculate a percentage discount in your head, divide the percentage by 10 to find 10% of the price, multiply that by the tens digit, and subtract the discount from the original total. For example, for 20% off $80, 10% is $8.00, so 20% is $16.00, leaving a final price of $64.00.
What is the standard formula for cross-multiplication in proportions?
The standard formula for cross-multiplication in the proportion A/B = C/D is A × D = B × C. To solve for any unknown variable, multiply the two known diagonally opposite values and divide by the third remaining value.
How does the tip calculator handle uneven cents when splitting a check?
The tip calculator calculates the exact total with tip to the nearest cent, divides equally across all party members, and explicitly allocates any remaining 1-cent difference to the first diner so the sum of individual shares matches the receipt exactly.