Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
Age
20 years, 0 months, 0 days
Years
20
Total days
7,305
Psst — share this and help Rex grow
One click, a permanent link with your numbers baked in.
How to use this
- 1Enter date of birth.
- 2Enter age on.
- 3Read your age on the right — it updates as you type.
- 4Hit Share to keep the scenario or send it to someone.
About this calculator
Pick a date of birth and a target date — get the exact age and total days lived.
Worked example
Using the values the calculator loads with:
Inputs
- Date of birth: 1990-01-01
- Age on: 1970-01-01
Results
- Age: 20 years, 0 months, 0 days
- Years: 20
- Total days: 7,305
What each field means
Inputs
- Date of birth
- The reference date for this calculation. Defaults to today unless you change it.
- Age on
- The reference date for this calculation. Defaults to today unless you change it.
Results
- Age
- Returned as a plain value and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Years
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Total days
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How does the age calculator work?
Pick a date of birth and a target date — get the exact age and total days lived.
What do I need to enter?
2 values: date of birth, and age on. Each field starts with a sensible default, so you can change one number at a time and watch the result move.
What does the age result mean?
It is returned as a plain value and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds.
Is this calculator free, and do I need an account?
Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser.
How accurate is the result?
It applies the standard formula exactly, so the arithmetic is precise. Estimates assume standard, average conditions — local rules, pricing, and materials vary.
Who is this tool for?
It's built for anyone doing everyday planning maths — a quick estimate that would otherwise need four browser tabs and a calculator app.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Age Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/age
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/age" target="_blank" rel="noopener">Age Calculator — RevenueLab</a> (2026).</p>
Source: [Age Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/age) (2026).