humanedose.com — Human Equivalent Dose Calculator

HED Calculator

FDA Guidance-aligned BSA normalization (Km method) with allometric check

Species

Km auto-fills. Weight editable.

Animal dose (mg/kg)

Animal weight (kg)

Human weight (kg)

Safety factor (for MRSD)

Human dose (mg/kg) — optional reverse

Human Equivalent Dose (Km)

— mg/kg

— mg total for 60 kg

HED = dose × (Km_animal / 37)

MRSD with safety factor

— mg

Total dose; divide by weight for mg/kg

Dose in mg/m²

— mg/m²

Animal = Human after normalization

Allometric check (W^0.33)

— mg/kg

Independent of Km

Why BSA, not body weight?

Physiology scales with surface area. Basal metabolic rate, cardiac output, and renal/hepatic clearance correlate with BSA (≈ W^0.67), not linear weight.
mg/kg alone over-predicts. Direct translation from mouse to human can overestimate by ~12×; Km correction aligns exposure.
Regulatory expectation. FDA Guidance for Industry (2005) recommends BSA normalization for small-molecule FIH dose selection from NOAEL.

FDA Method

HED (mg/kg) = Animal dose (mg/kg) × ( Km_animal / Km_human )

Km = body weight (kg) ÷ BSA (m²). Human Km = 37 (60 kg / 1.62 m²). Calculate HED in mg/kg, then convert to total mg: HED_total = HED_mg/kg × human weight.

K_m Reference Table

Species	Weight (kg)	BSA (m²)	Km

Values per FDA 2005; typical laboratory weights. Edit weight in calculator for your study.

Important Limitations

Biologics >100 kDa: Use target-mediated PK/PD and MABEL, not Km scaling.
Route-dependent: Topical, inhalation, ocular, and depot SC/IM require route-specific corrections.
Pediatric scaling: Do not scale from adult HED by weight alone; use PBPK/allometry and ontogeny.
Immunotherapies: For high-risk modalities, MABEL supersedes NOAEL/HED per EMA/FDA guidance.

References FDA Guidance for Industry: Estimating the Maximum Safe Starting Dose in Initial Clinical Trials (2005); Nair & Jacob, J Basic Clin Pharm 2016.

HED Calculator

Human Equivalent Dose (Km)

MRSD with safety factor

Dose in mg/m²

Allometric check (W^0.33)

Animal Equivalent Dose (reverse)