Creatinine Clearance (CrCl) Calculator – Cockcroft–Gault
Calculate adult creatinine clearance (CrCl) with the Cockcroft–Gault equation using age, an explicit weight basis, serum creatinine, and the published sex coefficient.
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About
This adult creatinine clearance calculator reproduces the 1976 Cockcroft–Gault equation from age, a published sex coefficient, serum creatinine, and an explicitly selected weight basis. The original report derived the equation in 249 men ages 18–92 and proposed a female coefficient of ×0.85. [1]
The output is estimated creatinine clearance (eCrCl) in mL/min. It is not indexed eGFR, a timed-urine measurement, measured GFR, CKD staging, or a medication dose.
Actual body weight is the original equation term. An alternative weight is accepted only when an applicable external protocol already specifies the numerical weight; this page does not infer IBW, AjBW, LBW, or another dosing weight. [8, 9]
Formula
Interpretation
| Measure | What it represents | Unit | Calculated here |
|---|---|---|---|
| Cockcroft–Gault eCrCl | Historical formula estimate of creatinine clearance | mL/min | Yes |
| 24-hour measured CrCl | Timed urine creatinine, urine volume, serum creatinine, and collection duration | mL/min | No |
| Indexed eGFR | Modern estimate of GFR standardized to 1.73 m² | mL/min/1.73 m² | No |
| Measured GFR | Exogenous filtration-marker measurement | mL/min or indexed units | No |
- Measure
- Cockcroft–Gault eCrCl
- What it represents
- Historical formula estimate of creatinine clearance
- Unit
- mL/min
- Calculated here
- Yes
- Measure
- 24-hour measured CrCl
- What it represents
- Timed urine creatinine, urine volume, serum creatinine, and collection duration
- Unit
- mL/min
- Calculated here
- No
- Measure
- Indexed eGFR
- What it represents
- Modern estimate of GFR standardized to 1.73 m²
- Unit
- mL/min/1.73 m²
- Calculated here
- No
- Measure
- Measured GFR
- What it represents
- Exogenous filtration-marker measurement
- Unit
- mL/min or indexed units
- Calculated here
- No
These measures are not interchangeable. Creatinine is filtered and also secreted by renal tubules, so measured creatinine clearance is not measured GFR; timed urine collection also introduces collection error. [6] This page does not assign a CKD G category or convert eCrCl into a dose or treatment conclusion.
How this Cockcroft–Gault calculator works
Enter age, choose the published male or female coefficient, identify the weight basis, and enter weight and serum creatinine with explicit units. The runtime normalizes lb to kg and µmol/L to mg/dL without intermediate rounding, applies the single 1976 equation, and rounds only the displayed eCrCl to one decimal place.
The Calculation audit preserves submitted values, runtime-normalized values, the raw runtime result, and the displayed result so the estimate can be inspected without a second formula implementation.
Which weight should be used in Cockcroft–Gault?
| Weight option | What it means here |
|---|---|
| Actual body weight | The original published equation term |
| Protocol-specified alternative | A numerical weight already required by an applicable external protocol |
- Weight option
- Actual body weight
- What it means here
- The original published equation term
- Weight option
- Protocol-specified alternative
- What it means here
- A numerical weight already required by an applicable external protocol
Later studies found that bias varies across body-size groups and substituted weight definitions; they do not establish one universal automatic selection rule. [8, 9, 11] This page does not select IBW, AjBW, LBW, obesity dosing weight, or another method.
If a current label or institutional protocol explicitly requires a named reference weight, use that external instruction. The separate Devine IBW and AjBW40 calculator can calculate those named models without sending or carrying values into this page; its use does not establish applicability here.
Creatinine clearance vs eGFR
Cockcroft–Gault estimates creatinine clearance in mL/min and contains a weight term. CKD-EPI eGFR estimates GFR and is normally reported in mL/min/1.73 m²; it was validated against measured GFR rather than measured creatinine clearance. The quantities cannot be simply interchanged, and Cockcroft–Gault eCrCl must not be assigned a KDIGO G category.
Use the separate Adult eGFR Calculator when CKD-EPI eGFR is the named task. The appropriate kidney-function measure depends on applicable labeling or protocol together with current institutional and clinical guidance; this calculator does not choose the measure, medicine, or dose. [3, 6]
Estimated CrCl vs 24-hour measured creatinine clearance
This page estimates CrCl from age, weight, serum creatinine, and the historical coefficient. A 24-hour measured creatinine clearance instead uses timed urine creatinine, urine volume or collection, serum creatinine, and collection duration; this page does not collect those urine data or calculate that separate test.
Measured CrCl is also not measured GFR because creatinine undergoes tubular secretion, and an incomplete or inaccurate timed urine collection can distort the result. [1, 6]
Is there a normal creatinine clearance range?
This calculator does not define a universal normal eCrCl range. Laboratory reference intervals for measured CrCl are not the same as a Cockcroft–Gault estimate, and age is already a mathematical input to this historical equation. An estimated CrCl should not be converted into a KDIGO G category or treated as a stand-alone CKD diagnosis.
Why Cockcroft–Gault is still used—and why practice is changing
Cockcroft–Gault remains relevant when a historical study, existing product label, or institutional protocol explicitly names eCrCl. Labels have used serum creatinine, measured CrCl, Cockcroft–Gault, MDRD, and CKD-EPI, so this page does not assume one method for every medicine. [6, 11]
FDA’s March 2024 final guidance recommends eGFR over Cockcroft–Gault eCrCl for determining renal function in renal-impairment pharmacokinetic studies. That study-design guidance does not mean every existing product label has already been rewritten to require eGFR. [2, 7]
NKF now advocates transition toward race-agnostic CKD-EPI eGFR for adult medication-related decisions. On June 1, 2026, NKF and U.S. pharmacy organizations announced support for that transition; on July 20, 2026, NKF announced the IMeD-eGFR implementation community to help organizations carry it out. [3, 4, 5] This calculator remains a transparent historical-equation tool, not a claim that Cockcroft–Gault is universally preferred in 2026.
When Cockcroft–Gault may be less reliable
- AKI or rapidly changing serum 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, and unusual body size can make the weight term difficult to interpret. [8, 9]
- Ages 93–139 are outside the original 18–92 derivation range.
- The equation predates modern serum-creatinine assay standardization. [2, 11]
These limitations do not identify an automatic replacement method for an individual; the relevant clinical workflow determines whether another estimate or measurement is needed.
Why low creatinine is not automatically rounded
Automatically replacing a positive serum creatinine with 0.8 or 1.0 mg/dL changes the submitted laboratory value. A comparison with measured 24-hour CrCl found that such rounding did not improve bias or accuracy. [8]
The runtime therefore uses the entered positive value without a floor. This arithmetic policy does not remove interpretation limits related to muscle mass, frailty, nutrition, assay methods, or unstable kidney function.
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, limitations, and transition to race-agnostic eGFR for medication-related decisions.
- National Kidney Foundation. Race-agnostic eGFR for Medication-related Decisions in Adults.
- National Kidney Foundation. National Kidney Foundation and U.S. Pharmacy Organizations Call for Transition to Race-Free eGFR in Medication Decision-Making. June 1, 2026.
- National Kidney Foundation. National Kidney Foundation Launches National Community to Advance Race-Agnostic Kidney Function Assessment for Medication-Related Decisions. July 20, 2026.
- 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. Final 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
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]
Studies and protocols have used different alternative weight definitions, with performance varying by body-size group and population. There is no universal automatic IBW, AjBW, LBW, or obesity-weight rule for every use. Enter an alternative only when a current applicable protocol explicitly requires it.
No. This page estimates CrCl from age, weight, serum creatinine, and the historical coefficient. A measured CrCl uses timed urine creatinine, urine volume or collection, serum creatinine, and collection duration, and can be affected by collection error and tubular creatinine secretion.
Automatic rounding changes the submitted laboratory value. This calculator uses the entered positive serum creatinine without a floor; a comparison with measured 24-hour CrCl found that rounding low creatinine did not improve bias or accuracy.
Sources: [8]
No. Existing labels and protocols use different kidney-function measures, and some older labeling reflects methods used when the product was studied. FDA’s 2024 renal-impairment guidance recommends eGFR over Cockcroft–Gault eCrCl for pharmacokinetic studies, while current NIDDK and NKF resources support contemporary race-agnostic eGFR approaches for adult medication-related decisions in appropriate settings. This calculator does not decide which measure, medicine, or dose applies to an individual workflow.
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Disclaimer
Educational and informational reference only. Not intended to replace professional medical advice, diagnosis, treatment, or independent verification.