This creatinine clearance calculator applies the Cockcroft-Gault equation — the estimate behind most medication dosing references — from age, weight, sex and serum creatinine.
CrCl vs eGFR — Two Estimates, Two Jobs
Cockcroft-Gault (1976) estimates creatinine clearance in mL/min and includes weight — drug labels and dosing references were built on it for decades, so pharmacists still reach for it first. eGFR (CKD-EPI), indexed to body surface area (mL/min/1.73 m²), is the modern staging measure for kidney disease — that is our GFR Calculator‘s equation. The two can differ meaningfully in the same patient (age extremes, obesity, muscle mass), and which one governs depends on the question: staging favors eGFR; many drug monographs still specify CrCl thresholds. Part of our Health Calculators collection.
Worked Examples (Verified)
- Man, 60 years, 80 kg, creatinine 1.2: (140−60) × 80 ÷ (72 × 1.2) = 74.1 mL/min
- Woman, 60 years, 65 kg, creatinine 1.0: same shape × 0.85 = 61.4 mL/min — the 0.85 factor approximates lower average muscle mass (creatinine’s source)
- Why weight matters here: the same man at 100 kg computes 92.6 mL/min — creatinine generation scales with muscle, which total weight only loosely tracks; at weight extremes clinicians adjust, cap, or measure directly (24-hour urine or cystatin C)
Where the Equation Strains
- Unstable creatinine: in acute kidney injury the level is a moving target and no steady-state formula applies.
- Extremes of muscle: bodybuilders read “worse,” amputees and cachectic patients “better,” than their true filtration.
- Age: validated in adults; the (140 − age) term makes very elderly estimates small — often correctly, since clearance genuinely declines ~1 mL/min/year after 40 in population data.
Related Tools
- GFR Calculator — CKD-EPI 2021 eGFR for staging
- Body Surface Area Calculator — the indexing denominator for eGFR
- Health Calculators — the full collection
Frequently Asked Questions
How is creatinine clearance calculated?
Cockcroft-Gault: CrCl = (140 − age) × weight (kg) ÷ (72 × serum creatinine), times 0.85 for women. A 60-year-old, 80 kg man at creatinine 1.2 gets ≈ 74 mL/min.
What is a normal creatinine clearance?
Young healthy adults run roughly 90–130 mL/min; values decline with age. Below 60 suggests reduced kidney function; dosing thresholds for many drugs sit at 50, 30 and 15 mL/min.
Why do drug labels use CrCl instead of eGFR?
History and evidence: the pharmacokinetic trials behind most labels measured or estimated Cockcroft-Gault clearance. Regulators have been modernizing guidance, but the monograph on the bottle remains the operative document — pharmacists reconcile any mismatch.
Should I use actual or adjusted body weight?
In obesity, actual weight overestimates clearance; many institutions use adjusted body weight (ideal + 0.4 × excess) or cap the creatinine. This calculator uses the weight entered, and its notes flag the issue — dosing decisions belong to the prescriber and pharmacist.
Can I measure clearance directly?
Yes — a timed (usually 24-hour) urine collection with a paired blood sample measures creatinine clearance without the estimation equations, and cystatin C-based eGFR offers an independent estimate when muscle mass makes creatinine unreliable.
Is this creatinine clearance calculator free?
Yes — free and instant, for information and education; it does not dose medication.