Math & Everyday
How to Calculate a Tip (and Split the Bill)
A fast mental method for 15%, 18%, and 20% tips — plus how to split the total across the table.
Math & everyday calculators
The quick calculations you reach for every day
Percentages, dates, tips, and discounts — answered instantly with a clean, no-clutter interface. No app, no sign-up, no math in your head.
Percentages
Find a percentage, a part of a whole, or the change between two numbers.
Dates & age
Exact age in years, months, and days, plus totals in weeks and days.
Money math
Split a tip across a table or price out a stacked clearance discount.
The tools
4 math & everyday calculators
Small calculations, done right
Some math comes up constantly: what's 15% of the bill, how old is someone to the day, what's the sale price after stacked discounts, what percentage did a number change. These are simple in theory and easy to fumble in the moment. Our everyday calculators give you the answer in one step.
Each tool is deliberately focused — one job, clearly laid out, with the result and the supporting numbers shown together. They work on your phone at a restaurant or on your laptop at a desk, and like everything on Smart Cost Hub they run instantly in the browser.
Browse the tools below, and check the guides for the formulas behind them so you can do the math yourself when you need to.
Guides
Read up on math & everyday
Math & Everyday
How to Calculate Exact Age in Years, Months, and Days
Counting age precisely means handling different month lengths and leap years. Here's the method behind it.
Math & Everyday
How to Calculate Percentages (3 Common Cases)
Find a percentage of a number, figure out what percent one number is of another, or calculate percent change.
Frequently asked questions
- Do these work on mobile?
Yes — every calculator is responsive and works in any modern phone or desktop browser, with no app to install.
- Will you add more everyday calculators?
Yes. This category grows over time — fractions, unit conversions, and more are on the roadmap.
- Is there any catch?
None. The tools are free, require no sign-up, and run entirely in your browser.