Convert animal age to human-equivalent age across mouse, rat, and zebrafish. Cross-species comparison, bidirectional conversion, strain-specific lifespan factors, and life-stage classification.
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Equivalent biological age across all species (anchored to 28 human years)
| Species | Strain | Age (days) | Age (months) | Life Stage | Lifespan % |
|---|---|---|---|---|---|
| Mouse(input) | C57BL/6J | 126 | 4.1 | Young adult (6 wk–6 mo) | 16% |
| Rat | Sprague-Dawley | 328 | 10.8 | Mature adult (6–12 mo) | 36% |
| Zebrafish | AB | 311 | 10.2 | Young adult (3–12 mo) | 24% |
When to use
Do not use for
Each species model is calibrated against published developmental milestones. The comparison is most reliable at well-studied anchor points (puberty, sexual maturity, middle age) and less reliable at extremes.
A 12-month BALB/c mouse and a 12-month C57BL/6J mouse get the same human-equivalent age. The strain factor only adjusts where each sits on its own lifespan curve.
Zebrafish development is temperature-dependent. The hpf-to-days conversion assumes standard conditions (28.5°C). Lower temperatures slow development; higher temperatures accelerate it.
Animal → human → animal conversions return the original value because all scaling models are piecewise-linear and analytically invertible.
Each species uses a piecewise-linear function mapping animal-days to human-equivalent days. The function is defined by segments with different ratios reflecting developmental phases (rapid juvenile growth → slower adult aging). Reverse conversion analytically inverts the piecewise function. Cross-species comparison converts to human-equivalent years as a common denominator, then back-calculates to each species.
Published 2026-04-09. Calculations support planning and documentation; verify procurement decisions against manufacturer specifications or institutional SOPs.
ConductScience Lab Animal Age Converter. ConductScience, Inc. 2026. Available at: https://conductscience.com/tools/animal-age-converter
Dutta S, Sengupta P. Men and mice: Relating their ages. Life Sciences. 2016;152:244-248.
Sengupta P. The Laboratory Rat: Relating Its Age With Human's. Int J Prev Med. 2013;4(6):624-630.
Kishi S et al. The zebrafish as a vertebrate model of functional aging. Exp Gerontol. 2003;38(7):777-786.
Multi-model aging studies are increasingly common, but comparing cohorts across species requires standardized age equivalence. A "middle-aged" mouse (12 months) is not the same biological age as a "middle-aged" rat (12 months) or zebrafish (18 months).
This calculator provides a common denominator — human-equivalent age — so you can design comparable cohorts across species. Enter your age in any species and see the equivalent in all others.
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