Creatinine Clearance Calculator (Cockcroft-Gault)
This creatinine clearance calculator estimates CrCl in mL/min with the original Cockcroft-Gault formula – for actual, ideal and adjusted body weight side by side. Example: a 60-year-old man weighing 80 kg with a serum creatinine of 1.2 mg/dL has a creatinine clearance of about 74.1 mL/min.
How it is calculated
Creatinine clearance (CrCl) is the volume of blood plasma the kidneys clear of creatinine per minute. The Cockcroft-Gault formula estimates it from a single blood value plus age, weight and sex. Published in 1976, it is still the formula many drug labels refer to for dose adjustment in reduced kidney function.
Formula
CrCl (mL/min) = (140 − age) × weight in kg ÷ (72 × serum creatinine in mg/dL); for women the result is multiplied by 0.85 (“15% less in females” in the original paper). Creatinine in µmol/L is first divided by 88.4. Unlike eGFR, the result is not normalised to 1.73 m² of body surface area – a larger person gets a larger value.
Worked example
Man, 60 years, 80 kg, 175 cm, creatinine 1.2 mg/dL: CrCl = (140 − 60) × 80 ÷ (72 × 1.2) = 6400 ÷ 86.4 = 74.1 mL/min. A woman aged 72 weighing 60 kg with 0.9 mg/dL comes to (140 − 72) × 60 ÷ (72 × 0.9) × 0.85 = 53.5 mL/min.
Which weight: actual, ideal or adjusted?
The original study used actual body weight. In people with overweight this overestimates clearance, because fat tissue produces hardly any creatinine. Two alternatives are therefore common:
- Ideal body weight (Devine): 50 kg for men or 45.5 kg for women, plus 2.3 kg for every inch of height above 5 feet. For 175 cm (68.9 in) that is 50 + 2.3 × 8.9 = 70.5 kg, giving 65.2 mL/min in the example.
- Adjusted body weight: ideal weight + 0.4 × (actual − ideal weight). Here 70.5 + 0.4 × 9.5 = 74.3 kg, giving 68.8 mL/min.
A comparison with measured 24-hour clearance in 3,678 patients (Winter et al., 2012) found the least bias with actual weight in underweight patients, ideal weight in patients of normal weight and adjusted weight (factor 0.4) in overweight and obese patients. The table marks the matching row by BMI; which weight applies in a given case is decided by the prescriber or the drug label.
CrCl or eGFR?
Both are estimates of kidney function from creatinine, but they are not interchangeable. eGFR (CKD-EPI 2021) is the standard for detecting and staging chronic kidney disease. Cockcroft-Gault remains in use mainly because many dosing recommendations were developed with it; the US National Kidney Foundation now recommends moving towards eGFR for these decisions as well. If you want the kidney stage G1–G5, use the GFR calculator.
Frequently asked questions
What is a normal creatinine clearance?
There is no single cut-off that fits everyone, because the value is not adjusted for body size and falls with age – the formula itself subtracts age from 140. Laboratories state their own reference ranges; chronic kidney disease is staged with the eGFR instead.
Which body weight should I use in Cockcroft-Gault?
The original formula uses actual weight. In a large comparison study, ideal body weight fitted best for people of normal weight and adjusted body weight (ideal + 0.4 × the excess) for people with overweight. For 80 kg and 175 cm the three results are 74.1, 65.2 and 68.8 mL/min.
Why is the result multiplied by 0.85 for women?
Women have, on average, less muscle mass and therefore produce less creatinine. Cockcroft and Gault accounted for this with a flat 15% reduction; it was an estimate, not a measured factor.
How do I convert creatinine from µmol/L to mg/dL?
Divide by 88.4: 106 µmol/L is 1.2 mg/dL. The calculator converts automatically when you switch the unit.
What is the difference between creatinine clearance and eGFR?
Cockcroft-Gault gives an absolute clearance in mL/min and includes body weight. eGFR by CKD-EPI is normalised to 1.73 m² of body surface area and does not use weight. For the same person the two numbers can differ noticeably.
Sources and legal basis
- Cockcroft-Gault 1976: Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron 1976;16(1):31–41 (original formula: Ccr = (140 − age) × weight ÷ (72 × Scr), women 15% less), doi:10.1159/000180580
- Winter MA, Guhr KN, Berg GM. Impact of various body weights and serum creatinine concentrations on the bias and accuracy of the Cockcroft-Gault equation. Pharmacotherapy 2012;32(7):604–612 (actual, ideal and adjusted body weight with a factor of 0.4), doi:10.1002/j.1875-9114.2012.01098.x
- Pai MP, Paloucek FP. The origin of the "ideal" body weight equations. Ann Pharmacother 2000;34(9):1066–1069 (ideal body weight according to Devine), doi:10.1345/aph.19381
- Dessein PH, Hsu HC, Tsang L, et al. Kidney function, endothelial activation and atherosclerosis in black and white Africans with rheumatoid arthritis. PLoS One 2015;10(3):e0121693, Table 1 (formulas written out: Cockcroft-Gault with factor 0.85; ideal body weight 50 or 45.5 kg + 0.906 kg per cm above 152.4 cm)
- National Kidney Foundation: Cockcroft-Gault formula (classification: recommendation to switch to eGFR equations for dosing decisions)
As of: · Editorial policy
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