Everyday calculators for dates, fractions, percentages and more. Get a plain answer in seconds and move on.
Your date result
Find the one that matches the number you're stuck on.
Days between dates, or add and subtract days.
Get my answer →Your exact age in years, months and days from your birthday.
Get my answer →Percent of, percent change and more. Four answers from two numbers.
Get my answer →Split the bill and figure the tip in seconds.
Get my answer →Add, subtract, multiply and divide fractions with instant results.
Get my answer →Find the percentage increase between two values instantly.
Get my answer →Hours and minutes between two times, or add time to a clock.
Get my answer →Calculate the percentage change between any two numbers.
Get my answer →Convert numbers to Roman numerals and back.
Get my answer →See the sale price and how much you save at any discount.
Get my answer →Final price after a percentage off, fast.
Get my answer →Life path and destiny numbers from name and date.
Get my answer →Calculate how much something dropped as a percentage.
Get my answer →See how much Robux you keep after the 30% marketplace fee, plus USD value at the DevEx rate.
Get my answer →Every calculator on this site runs the same formula a teacher would put on a whiteboard. Nothing is looked up, nothing is estimated from a database. Take the percentage tool: it multiplies your first number by the second, divided by 100, for "A% of B," and it flips that around, dividing A by B and multiplying by 100, to answer "what percent is A of B." Percentage change is the classic (new minus old) divided by old, times 100, with a negative sign meaning the number went down. Type 25 and 200 into that calculator and you get 12.5 as the answer to "25% of 200," and 87.5% as the answer to "how much did 25 change to reach 200." Same two inputs, four different questions answered at once, because the underlying arithmetic doesn't change, only which piece you're solving for.
The discount calculator works off that same percentage math with one extra step. Enter an $80 item at 25% off and the tool multiplies 80 by (1 minus 0.25), which is 80 times 0.75, landing on a $60 sale price and $20 saved. Add a sales tax rate and it applies that to the discounted price, not the original, because tax is charged on what you actually pay. This is also where a lot of mental math goes wrong at checkout: two discounts don't add together. A 20% markdown followed by another 10% off is not 30% off. It's 0.80 times 0.90, which works out to 28% off the original price, a difference that gets bigger the more discounts get stacked. The fraction calculator runs on the same principle of doing the real operation instead of a shortcut: common denominators for addition and subtraction, straight cross-multiplication for multiplying, and flipping the second fraction to divide, then reducing by the greatest common divisor so 2/4 always comes back as 1/2.
Most of these tools return more than one number, and the labels tell you which question each one answers. The percentage calculator's four results are not four different calculations bundled for convenience. They're the four ways two numbers can relate to each other as a percent, and the row labels ("A% of B," "A is what % of B," "% change A to B") map directly onto the formulas above. The date calculator does the same thing for time: ask for days between two dates and it gives you the raw day count, the same span broken into weeks and leftover days, and an approximate month count using an average month length of 30.44 days, which is why that last figure is always described as approximate while the day and week counts are exact.
The tip calculator is the one where people second-guess the math after the fact. Eighteen percent of a $60 bill is $10.80, for a $70.80 total split however many ways you set it to. Standard US table-service tipping runs 15 to 20 percent of the bill, and most people calculate it against the pre-tax amount, though tipping on the post-tax total isn't wrong, it's just a slightly bigger tip on the same meal. If a number looks off, it's almost always because a rate or an input got typed wrong, not because the formula changed. Every field updates live as you type, so you can walk backward through an answer that surprised you and see exactly which input moved it.
A calculator is faster for compound situations. Splitting a bill four ways with an 18% tip, running a percentage change on quarterly numbers, or reducing an odd fraction like 14/35 all involve more than one step, and it's easy to drop a step doing it by hand. But some percentage math is fast enough that opening a tool costs more time than it saves. 10% of any number just moves the decimal point one place left. 50% is half. 25% is a quarter, so 25% of 80 is 20 before you've finished reading the sentence. The break-even point is usually two operations: if you need to find a percentage and then add or subtract it from something else, that's when a typo becomes expensive and a calculator earns its keep.
The same logic applies across every tool here. Roman numerals, numerology, and Robux tax conversion aren't things most people memorize the rules for, so a calculator isn't a convenience there, it's the only practical way to get the number without cross-referencing a chart. Percentage and fraction math, by contrast, is math most people already learned; the calculator just removes the risk of arithmetic slipping under time pressure. Use the shortcut in your head when the numbers are round and the operation is single-step. Reach for the tool the moment a second step gets involved.