About This Site

This site exists because almost every dog age calculator online does the same two things: it hides which formula it is using, and it prints a single confident number. Both are avoidable. This one shows you two independent estimates, names the source of each, and tells you where each one stops being valid.

It is built and maintained by an independent developer who builds small, focused web tools. It is not run by a veterinary practice, and nothing here is veterinary advice.

The two methods

• Epigenetic clock: human age = 16 × ln(dog age) + 31, from a 2020 UC San Diego study published in Cell Systems that compared DNA methylation patterns in Labrador retrievers and humans. Valid from one year of age; below that we interpolate and label it as an approximation.
• Veterinary rule of thumb: about 15 human years for the first dog year, about 9 more for the second, then a size-dependent increment per year. A clinical shortcut, not a research finding, but it captures the strong effect of body size that the epigenetic formula ignores.

Accuracy principles

These are the rules the whole site is built on:

• No invented statistics. If a figure is not something we can point to a source or a stated method for, it does not appear.
• Ranges over false precision. Where a method is genuinely a range — large breeds gaining +5 to +6 human years per dog year — we print the range. Results are rounded to whole years because the underlying methods do not support decimals.
• Every formula is labelled. You should always be able to tell which method produced a number and what its limits are.
• Honest failure modes. The epigenetic formula is undefined below one year, so we say so instead of quietly printing something plausible.
• No health claims. Life-stage labels are conventions used to prompt conversations with a vet, not diagnoses.

Your data

The calculator runs entirely in your browser. There is no account, no server-side computation and no analytics on the values you type — the age and size you enter never leave your device. Details are in the privacy policy.

Corrections

If you spot an error in the arithmetic, the description of a method, or a statement that overreaches what the evidence supports, please tell us — corrections are welcome and get made. Use the contact page.