A little clarity for everyday life.

Callculus is a collection of free online calculators for the questions that come up while planning, learning, building, and writing. You can use every tool without creating an account or installing an app.

One place for your next calculation

Explore 70 tools across seven categories. Work out a percentage, estimate project materials, check a component value, or count the words in a draft.

• Money & finance — Plan payments, compare percentages, and explore investment growth.
• Health & fitness — Understand body measurements and estimate your daily energy needs.
• Math & everyday — From a quick conversion to geometry homework, find your next answer.
• Electronics — Work out component values and explore the numbers behind your circuit.
• Construction — Estimate materials for flooring, walls, and concrete projects.
• Text tools — Count, analyze, and transform your writing in your browser.
• Image tools — Turn images into data for your next microcontroller project.

Understand the numbers

Calculator pages include explanations of their inputs, formulas, or use cases. Check units and assumptions before using a result. Estimates and rounded values have limits, and a calculator cannot account for every real-world circumstance.

Health and financial results are informational. They are not a diagnosis, a treatment recommendation, or personalized financial advice.

Free, supported by advertising

Advertising helps keep these tools free. Read our privacy policy for information about analytics, cookies, and data handling.

Help us improve

If you find an issue or need a calculator we don’t yet offer, get in touch. Include a non-sensitive example so we can understand the problem.