Everything you might want to know about how our tools work.
About the Site
Yes — completely free, no account required, no subscription. Every calculator on the site is available to anyone at no cost.
No. All calculations happen entirely in your browser. Your date of birth, age, and any other inputs never leave your device and are never stored or transmitted to our servers.
We use Google Analytics to collect anonymous usage data — pages visited, time on site, general location (country level), and device type. We do not collect personally identifiable information. See our Privacy Policy for full details.
Calculator Accuracy
Age calculators (days, weeks, hours, etc.) are precise — they use exact date arithmetic accounting for leap years. Life stat calculators (heartbeats, miles walked, calories) are estimates based on statistical averages and the inputs you provide. They're designed to be interesting and roughly accurate, not medically precise.
We use published data from reputable sources including the CDC, WHO, NASA, OECD, American Heart Association, American Lung Association, and peer-reviewed research. Each calculator page links to its relevant sources. Formulas like dog years and cat years use standard veterinary guidelines.
No — and we're very clear about this on every relevant page. Life expectancy figures are population-level statistical averages. They cannot account for your individual genetics, health, lifestyle, or future medical advances. They are designed to inspire reflection about time, not to make personal predictions.
Most sites use the outdated "multiply by 7" rule. Our dog years calculator uses a logarithmic formula based on epigenetic research published in Cell Systems by UC San Diego scientists — which more accurately reflects how dogs actually age biologically. We also offer the 7x method for comparison.
Using the Tools
Tools like "Age in Days" and "Days Left" calculate from your exact birth date to today's date, so they need your full date of birth for precision. Tools like "Heartbeats" only need your age in years, so we use a simpler input. None of this information is stored.
Absolutely — we love suggestions. Use our Contact page and select "Calculator suggestion." We read every message.
Please use our Contact page and select "Report an error." Include the calculator name and what you think is incorrect. We investigate and fix errors promptly.