STSApps

Calculator Tools

Fast math tools for quick decisions

Use these calculators to answer everyday percentage and campaign planning questions in seconds.

These calculators handle the number questions that slow you down day to day: how big a tip to leave, how to split a shared bill fairly, what a discount really comes to, and how much a figure changed over time. Each one focuses on a single task, so you get an answer in seconds without building a spreadsheet.

All of them are free, need no sign-up, and run in your browser, so your numbers stay on your device.

Percentage Calculator

Find percent of a number, compare values, and calculate percent change.

FairTab Group Expense Splitter

Split group expenses with no signup and get a simple settle-up plan.

UTMatic

Generate campaign URLs with structured UTM parameters.

How to choose

Reach for the percentage calculator for tips, discounts, and change over time. Use the expense splitter when several people share a bill and you want a fair settle-up. Pick UTMatic when you need a campaign link that reports cleanly in analytics.

Related guides

Frequently asked questions

Are these calculators free?
Yes. The percentage calculator, the expense splitter, and UTMatic are all free, with no sign-up and no cap on how many calculations you run in a session.
Do I need an account?
No. You can open any calculator and start entering numbers straight away, and none of these tools ask you to register or log in first.
Do they work on my phone?
Yes. Each calculator reflows for a small screen, so splitting a bill or working out a percentage on a phone is as quick as it is on a laptop.
Are my numbers saved?
No. The math runs in your browser as you type, and the figures you enter are not stored or uploaded, so closing the tab clears them.
Can I use decimals?
Yes. The calculators accept whole numbers and decimals, so you can enter an amount like 19.99 or a rate like 7.5 percent without rounding first.