About Dayob

Dayob builds free, fast calculators for everyday questions, and explains the math behind every answer so you can trust it, check it and learn from it.

Why we built it

Most people search for a calculator in the middle of a real task: standing in a garden center deciding how much gravel to buy, the night before a final exam, or comparing two savings options. Many calculators online give a bare number with no explanation, hide the assumptions they use, or bury the tool under pop-ups. We wanted the opposite: a clean tool that loads instantly, states its assumptions, and is followed by a guide written in plain English.

How our calculators are made

• Formulas from standard references. Each calculator uses published definitions and formulas, and links to the official source it relies on, such as NIST for unit conversions, the IRS for retirement limits, or the College Board for AP exam structure.
• Tested code. The math behind every tool lives in its own module with automated tests that check results against worked examples before each release.
• Honest about estimates. When a result depends on assumptions, such as gravel density or an AP score curve, we say so on the page and let you change the input.
• Reviewed and dated. Every calculator shows when it was last reviewed. Figures that change yearly, such as contribution limits, are checked when new values are published.

Editorial standards

Our guides are written and edited by the Dayob editorial team. We write original explanations, use worked examples we have checked by hand, and cite official sources. We do not accept payment to include or rank products. If we ever add affiliate links, they will be clearly labelled and will never change a calculator's result.

What Dayob is not

Our tools are for planning and learning. They are not a substitute for an engineer, accountant, financial adviser, physician or your teacher. For structural, legal, medical or major financial decisions, confirm the numbers with a qualified professional. See our disclaimer for details.

What's here today

Dayob currently offers 15 calculators across construction, math, education, science, fitness and finance, with new tools and guides added regularly. Browse all calculators or read the guides.

Contact

Found an error, or want a calculator we don't have yet? We read every message. Use the contact form or email contact@dayob.com.