Sumplain

Free online calculators and tools

Free online calculators for everyday decisions

Use practical calculators for finance, health, dates, work, developer tasks, and text—with clear formulas, private browser-based inputs, and useful guidance.

Popular tools

Start with frequently used calculators for money, health, dates, and work.

Browse by category

Find focused tools for a specific question or task.

Calculators that explain the result

Sumplain brings everyday calculators and browser-based utilities into one fast, searchable collection. Estimate compound interest, loan payments, mortgage costs, BMI, basal metabolic rate, dates, work hours, text length, and common developer formats without creating an account.

Each calculator shows its assumptions and adds plain-language guidance so you can understand what the number includes, what it leaves out, and which related tool may help next. Inputs are processed in your browser whenever the task can be completed locally.

Why use Sumplain?

A focused tool should be quick to use and clear about its limits.

Transparent methods

Formulas, units, assumptions, and exclusions are explained next to the result.

Private by design

Calculator and text inputs stay in your browser for tools that do not require a server.

Practical next steps

Related calculators, examples, and FAQs help you continue without starting over.