FreeNo sign-up. Runs in your browser.

Free online tools for time, dates, data, and code

Calculators, converters, and developer tools that run in your browser. Each page shows the formula it uses, so you can check the answer yourself.

  • Nothing leaves your device
  • Formula shown with every result
  • Worked examples are tested

Browse tools by category

Pick a category to see every tool in it, or jump straight to one of the tools below.

What you can do on Utilza

  • Calculators: add up hours, count days between dates or working days, fill in a weekly time card, find an exact age, and work out percentages and discounts.
  • Converters: switch data sizes between bytes, KB, MB, GB, and TB, and convert data between JSON, CSV, and YAML.
  • Developer tools: format and validate JSON, generate UUIDs and hashes, convert Unix timestamps, and encode or decode URLs and Base64.
  • Internet tools: estimate download times and turn Mbps into MB/s.

How the tools work

Every tool runs in your browser. The numbers, text, and files you enter are not uploaded, and nothing needs an account.

Each page explains the formula or rules behind the result and lists its limitations, so you can check an answer by hand. The worked examples on every page are also automated tests, and a release is stopped if a result and its example disagree.

All tools A–Z

The full list of Utilza tools in one place.