Published male coefficient
Age 60, actual weight 70 kg, and creatinine 1.0 mg/dL → raw 77.77777777777777 → displayed 77.8 mL/min.
Educational reference only. Not a diagnostic tool. See full disclaimer.
NephrologyCrCl
Cockcroft–Gault Creatinine Clearance Calculator
Estimate adult Cockcroft–Gault creatinine clearance in mL/min from an explicit weight basis, without automatic weight selection or a dosing recommendation.
Content updated: View sources
QuickMedCalc is developed and maintained by an independent developer. Medical content is not independently reviewed by a physician.
Formula and medical content are based on the references listed on this page. See sources, About, and Sources and Review Process.
About
This adult calculator transparently reproduces the 1976 Cockcroft–Gault estimate from age, a published sex coefficient, serum creatinine, and a weight term. The original report derived the equation in 249 men ages 18–92 and compared predictions with measured 24-hour creatinine clearance; its proposed female coefficient is ×0.85. [1]
Actual body weight is the original equation term. Because later studies have found different bias with different body-size definitions and populations, this page does not invent a universal automatic choice. “Protocol-specified alternative weight” means that an applicable protocol has already supplied the numerical weight to enter. [5, 6]
The output is estimated creatinine clearance (eCrCl) in mL/min. It is not indexed eGFR, measured CrCl, measured GFR, CKD staging, or a medication dose. Keeping this historical calculation available does not claim that it is generally preferable to modern race-free eGFR. [2, 3]
Formula
Published male coefficient: CrCl = [(140 − age in years) × submitted weight term (kg)] ÷ [72 × serum creatinine (mg/dL)]. [1]
Weight lb × 0.45359237 = kg; serum creatinine µmol/L ÷ 88.4 = mg/dL. The calculator does not derive a weight term or raise a low positive creatinine before applying the equation.
Interpretation
| Measure | What it represents | Unit | Calculated here |
|---|---|---|---|
| Cockcroft–Gault eCrCl | Historical formula estimate of creatinine clearance | mL/min | Yes |
| Measured CrCl | Timed urine and serum measurements | mL/min | No |
| Indexed eGFR | Modern GFR estimate standardized to 1.73 m² | mL/min/1.73 m² | No |
| Measured GFR | Exogenous filtration-marker measurement | mL/min or indexed units | No |
These four measures are not interchangeable. Creatinine is filtered and also secreted by renal tubules, so creatinine clearance and GFR are different concepts; timed urine collection also introduces collection error. [3] This eCrCl result is not assigned a CKD G category and cannot by itself produce a dose or treatment conclusion.
How the weight term is handled
The original equation includes body weight, and actual body weight is its published weight term. [1] Later comparisons substituted other body-size definitions and found that bias varied across weight groups and study populations rather than establishing one universal choice. [5, 6, 8]
This calculator therefore never derives ideal, adjusted, lean, or another weight. Select “protocol-specified alternative” only when the relevant protocol has already provided the value. Changing the selected basis or unit clears the weight so old digits cannot be silently reinterpreted; that is a software safeguard, not a clinical weight recommendation.
Units, precision, and display
Weight is normalized with 1 lb = 0.45359237 kg, and creatinine in µmol/L is divided by 88.4 to obtain mg/dL. Conversion occurs before calculation without intermediate rounding. The raw equation result remains at full floating-point precision and only the final display is rounded to one decimal place. A positive result below the 0.1 display boundary is shown as <0.1 mL/min, never as a false zero.
The accepted input range and strict ordinary-decimal format are software-validation boundaries, not physiological ranges or laboratory reference intervals.
Worked examples
Published female coefficient
The same age, weight, and creatinine with the ×0.85 coefficient → raw 66.11111111111111 → displayed 66.1 mL/min.
Equivalent units
70 kg and 154.3235835 lb, paired with 1.0 mg/dL and 88.4 µmol/L creatinine, normalize to equivalent inputs and the same 77.8 mL/min display.
Explicit alternative basis
Entering the same numerical weight under “protocol-specified alternative” preserves the arithmetic but labels the submitted basis. That label is not a recommendation to use an alternative weight.
These examples audit the implemented formula and unit paths; they do not interpret an individual result. [1]
Why the equation is still encountered
Cockcroft–Gault has a long history in pharmacokinetic research, some product labels, and some institutional protocols. Across current and historical sources, kidney-function descriptions have included serum creatinine, measured CrCl, Cockcroft–Gault, MDRD, and CKD-EPI; there is no single method required by every label. [3, 8]
The applicable current product label and protocol—not this general calculator—determine which measure is relevant. This page reproduces the equation but does not select a medicine, method, threshold, or dose.
Current limitations and modern context
The original model came from 249 men ages 18–92; the 0.85 female coefficient was proposed as a 15% adjustment and was later examined in older women. [1, 7] Ages 93–139 remain mathematically accepted here but are explicitly outside that derivation range.
The equation predates modern creatinine assay standardization. Comparisons that use standardized creatinine, different weight definitions, or measured GFR can produce different agreement. Measured CrCl is also susceptible to timed-urine collection error, and tubular creatinine secretion means it is not measured GFR. [3, 8]
NKF now supports transition toward race-free eGFR for medication-related decisions, and FDA’s 2024 pharmacokinetic guidance supports contemporary eGFR approaches rather than requiring Cockcroft–Gault for every study or label. [2, 4] This historical calculator remains available only for transparent reproduction when a current label or applicable protocol explicitly calls for it.
When the estimate may be unreliable
- AKI or rapidly changing creatinine can violate the stable-creatinine assumption.
- Very low or high muscle mass, frailty, malnutrition, amputation, paralysis, muscle wasting, bodybuilding, creatine supplementation, and recent meat intake can affect serum creatinine independently of filtration.
- Obesity, edema, ascites, extreme body size, and other settings in which the weight term is difficult to interpret can materially change the estimate. [5, 6]
- People outside the original derivation population, including ages above 92, require recognition as extrapolation.
For accuracy-critical decisions, narrow thresholds, unusual body size, or unreliable creatinine, current sources describe alternatives such as cystatin C-based estimates, measured CrCl, or measured GFR with an exogenous marker. [3, 4] This is static context, not an individualized instruction.
Why low creatinine is not rounded
Automatically replacing a positive serum creatinine with 0.8 or 1.0 mg/dL changes the submitted laboratory value. In a study comparing Cockcroft–Gault estimates with measured 24-hour CrCl, such rounding did not improve bias or accuracy. [5]
This implementation therefore uses the entered positive value without a floor. That arithmetic choice does not imply that low creatinine is free of interpretation limits related to muscle mass, frailty, nutrition, or other non-GFR determinants.
References
- Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron. 1976;16(1):31–41. PMID 1244564. DOI 10.1159/000180580.
- National Kidney Foundation. Cockcroft–Gault Equation for Estimating Creatinine Clearance: historical derivation and transition to race-free eGFR for medication-related decisions.
- NIDDK. Determining Drug Dosing in Adults with Chronic Kidney Disease.
- FDA. Pharmacokinetics in Patients with Impaired Renal Function — Study Design, Data Analysis, and Impact on Dosing. Guidance for Industry. March 2024.
- 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. PMID 22576791. DOI 10.1002/j.1875-9114.2012.01098.x.
- Demirovic JA, Pai AB, Pai MP. Estimation of creatinine clearance in morbidly obese patients. Am J Health Syst Pharm. 2009;66(7):642–648. PMID 19299371. DOI 10.2146/ajhp080200.
- Sokoll LJ, Russell RM, Sadowski JA, Morrow FD. Establishment of creatinine clearance reference values for older women. Clin Chem. 1994;40(12):2276–2281. PMID 7988015.
- Stevens LA, et al. Comparison of drug dosing recommendations based on measured GFR and kidney function estimating equations. Am J Kidney Dis. 2009;54(1):33–42. PMID 19446939. PMCID PMC2756662. DOI 10.1053/j.ajkd.2009.03.008.
FAQ
It estimates 1976 Cockcroft–Gault creatinine clearance (CrCl) in mL/min from age, the published sex coefficient, weight used in the equation, and serum creatinine. It is not measured creatinine clearance, measured GFR, eGFR, CKD stage, or a dose.
Sources: [1]
For the published male coefficient, CrCl = [(140 − age) × weight in kg] ÷ [72 × serum creatinine in mg/dL]. The published female coefficient multiplies that result by 0.85. This page converts lb to kg and µmol/L creatinine to mg/dL before calculation without rounding either input first.
Sources: [1]
Cockcroft–Gault estimates creatinine clearance in mL/min and includes a body-weight term. CKD-EPI eGFR estimates GFR indexed to 1.73 m². They can differ, especially with differing body size or creatinine determinants; the appropriate measure depends on the question, current label, and applicable protocol.
Actual body weight is the original Cockcroft–Gault equation term. This page requires that choice to be explicit rather than deciding a weight from BMI, age, sex, obesity, or body composition.
Sources: [1]
Automatic rounding changes the published input rather than calculating the submitted value. This page uses the entered positive serum creatinine without a floor or cap and presents limitations as static context.
Sources: [5]
The equation assumes serum creatinine is reasonably stable. Acute kidney injury or rapidly changing creatinine can violate that assumption.
Sources: [3]
No. Cockcroft–Gault CrCl is not a CKD diagnosis or G-category calculation. CKD assessment needs appropriate eGFR, albuminuria, chronicity, cause, and clinical context.
Sources: [2]
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Disclaimer
Educational and informational reference only. Not intended to replace professional medical advice, diagnosis, treatment, or independent verification.