OL Research supplies research materials exclusively for laboratory use. All products are handled and distributed in accordance with UK regulations governing research chemicals. We do not advise, support or condone the use of research chemicals in humans or animals.

Research Tools

🐁 Interspecies Dose Scaling Calculator — Preclinical to Clinical Translation

Free laboratory calculator for research use. Results display instantly in-browser — no data is transmitted.

Home › Research Tools › Interspecies Dose Scaling Calculator — Preclinical to Clinical Translation

About This Calculator

Translating doses between animal models and estimating human equivalent doses (HED) is a fundamental step in preclinical research design. The body surface area (BSA) method — using published Km factors — is the standard approach recommended by regulatory agencies for first-in-human dose estimation from animal data (FDA Guidance for Industry, 2005; Reagan-Shaw et al., FASEB J 2008).

The formula is: HED (mg/kg) = animal dose (mg/kg) × (animal Km ÷ human Km). The Km factor normalises body weight to body surface area for each species — smaller animals have proportionally larger surface areas relative to body weight, meaning they generally require higher mg/kg doses to achieve equivalent systemic exposure.

This calculator applies published Km values (mouse: 3, rat: 6, rabbit: 12, dog: 20, primate: 37, human: 37) and supports conversion in any direction — mouse to rat, rat to human, human to mouse, or any other pair. The output includes the conversion factor and a full method citation for use in research documentation.

Important: BSA-based scaling is a starting point for dose-range finding, not a definitive prediction of pharmacokinetic equivalence. Species differences in absorption, distribution, metabolism, and excretion (ADME) must be considered alongside allometric scaling.

Calculator

mg/kg
Scaled Dose
—mg/kg (target species)
—Conversion factor

Frequently Asked Questions

What is the Km factor and where do the values come from?
The Km factor is the ratio of body weight (kg) to body surface area (m²) for each species. Published values are: Mouse 3, Rat 6, Guinea pig 8, Rabbit 12, Dog 20, Monkey 37, Human 37. Source: Reagan-Shaw S, Nihal M, Ahmad N. Dose translation from animal to human studies revisited. FASEB J. 2008;22:659–661.
Why does a mouse need a higher mg/kg dose than a human?
Smaller animals have proportionally larger body surface areas relative to their body weight. Since many drug clearance mechanisms scale with BSA rather than body weight, smaller animals clear compounds faster per kg of body weight. A 10 mg/kg mouse dose typically equates to approximately 0.81 mg/kg in humans (factor: 3÷37 = 0.081 × 10).
Is Km-factor scaling accurate for all compounds?
BSA-based scaling is most accurate for compounds cleared primarily by renal filtration or metabolism proportional to BSA. It is less accurate for compounds with species-specific metabolism, active transport, protein binding differences, or nonlinear pharmacokinetics. Always supplement allometric scaling with in-vitro ADME data and species-specific PK modelling where available.
What is the FDA guidance on interspecies dose conversion?
The FDA's 2005 guidance document "Estimating the Maximum Safe Starting Dose in Initial Clinical Trials for Therapeutics in Adult Healthy Volunteers" recommends the BSA-based Km method for calculating human equivalent doses from animal NOAEL data. The guidance recommends applying a safety factor of 10 for first-in-human estimation.