Creatinine Clearance Cockcroft–Gault Calculator
Estimate adult creatinine clearance in mL/min with the historic Cockcroft–Gault equation, compare actual, Devine ideal, and adjusted body-weight inputs, and see how the selected estimate sits relative to a drug-label threshold.
Enter the adult dosing record
Cockcroft–Gault result
A mathematical margin is not permission to choose a dose. Confirm how the label defines renal function and whether the value is near a category boundary.
The selected estimate is above the entered 50 mL/min comparison point. The drug label, clinical context, trajectory, and pharmacist or prescriber determine any action.
What Cockcroft–Gault estimates
The 1976 Cockcroft–Gault equation predicts creatinine clearance from age, body weight, and serum creatinine. The original derivation related age and 24-hour creatinine excretion per kilogram in adult patients and compared predicted values with measured urinary creatinine clearances. A 15% lower value was proposed for females, now commonly implemented by multiplying the male-form equation by 0.85.
The output is an estimated creatinine clearance, often abbreviated eCrCl, in mL/min. It is not a direct measurement of glomerular filtration rate. Creatinine is filtered and also secreted by renal tubules, so measured creatinine clearance itself may exceed measured GFR. Muscle mass, diet, medications, assay calibration, amputation, paralysis, frailty, body size, and rapidly changing kidney function can all weaken a serum-creatinine equation.
Many older drug-development programs and labels used Cockcroft–Gault, but U.S. labels are not uniform. NIDDK notes that FDA does not endorse one specific estimating equation for every dosage adjustment. Labels may be based on measured creatinine clearance, Cockcroft–Gault, MDRD, CKD-EPI, serum creatinine, or study-specific definitions. The correct question is not simply “What is the CrCl?” but “Which kidney-function measure and body-size convention does this drug’s current label use?”
Equation and unit contract
The numerator falls with age and rises in direct proportion to the selected weight. The denominator rises with serum creatinine. Because weight is embedded directly, choosing actual, ideal, or adjusted weight can move the answer across a label cutoff even when every laboratory value is unchanged.
The calculator converts pounds to kilograms using 0.45359237 kg per pound. Height is used only to calculate Devine ideal body weight, adjusted body weight, and Mosteller body surface area. The selected Cockcroft–Gault output is not automatically indexed to 1.73 square meters. A contextual indexed value is displayed separately and must not be confused with laboratory-reported CKD-EPI eGFR.
The calculator does not round serum creatinine to 1.0 mg/dL. Published evidence does not support routine rounding as a universal practice, and it can substantially lower the estimate in older adults or people with low muscle mass. When creatinine production is atypical, a clinician may use cystatin C, measured clearance, a timed urine collection, exogenous filtration markers, or another approach.
Three body-weight spokes
Actual body weight
The current scale weight is closest to the weight term used in the original equation, but it can overestimate kidney function when a high body weight largely reflects adipose tissue. Some labels or institutional policies nevertheless specify actual weight.
Devine ideal body weight
For height at least 60 inches, this calculator uses 50 kg plus 2.3 kg per inch over five feet for the male coefficient and 45.5 kg plus 2.3 kg per inch for the female coefficient. “Ideal” is a historical dosing scalar, not a healthy-weight target.
Adjusted body weight
AdjBW equals IBW plus a selected fraction of actual weight minus IBW. The default 0.40 factor is shown for comparison; it is not universally correct. The factor, drug, and institution must agree.
If actual weight is below Devine IBW, this calculator does not let the adjusted formula create a value above actual weight; adjusted weight is shown as actual weight for that comparison. Height below 60 inches makes the reviewed Devine formula unavailable, so an IBW- or adjusted-weight selection is blocked rather than silently extrapolated.
Worked example: age 65, male coefficient, creatinine 1.2
- Convert weight. A current weight of 180 lb is 81.6 kg. A height of 70 inches is 10 inches above five feet.
- Build alternatives. Male Devine IBW is 50 + 2.3 × 10 = 73.0 kg. AdjBW0.4 is 73.0 + 0.4 × (81.6 − 73.0) = 76.5 kg.
- Apply Cockcroft–Gault. With actual weight, (140 − 65) × 81.6 ÷ (72 × 1.2) produces 70.9 mL/min.
- Compare spokes. The same equation gives 63.4 with IBW and 66.4 with AdjBW0.4. The 7.5-mL/min range is entirely from weight choice.
- Check the label boundary. The selected 70.9 result is 20.9 mL/min above an illustrative 50-mL/min cutoff. That arithmetic alone does not establish a dose.
The Mosteller body surface area for this example is about 2.008 m². Normalizing the selected estimate gives about 61.1 mL/min/1.73 m². That transformed Cockcroft–Gault number remains different in origin from CKD-EPI eGFR and should not be substituted into a label unless the relevant guidance supports it.
Do not collapse different kidney measures
| Measure | Typical unit | Key distinction |
|---|---|---|
| Cockcroft–Gault eCrCl | mL/min | Age, weight, creatinine, and historic sex coefficient; weight convention materially affects output. |
| CKD-EPI eGFR | mL/min/1.73 m² | Laboratory-reported filtration estimate normalized to standard body surface area; 2021 equations omit race. |
| De-indexed eGFR | mL/min | Laboratory eGFR multiplied by actual BSA and divided by 1.73; sometimes considered for dosing. |
| Measured creatinine clearance | mL/min | Uses timed urine creatinine and serum creatinine; vulnerable to collection error and tubular secretion. |
| Measured GFR | mL/min or normalized | Uses an exogenous filtration marker and specialized testing; closest to the intended physiologic quantity. |
NIDDK recommends considering more accurate methods when an estimate is near a drug cutoff, when body size is very large or small, or for narrow-therapeutic-index drugs. A result far from a threshold can still be misleading when creatinine is not at steady state.
Limits that matter before dosing
Serum creatinine lags behind an abrupt kidney injury. During a rapid rise, any steady-state equation may overestimate current clearance; during recovery, it may underestimate. Dialysis, extracorporeal therapies, pregnancy, critical illness, edema, amputation, neuromuscular disease, cachexia, very high muscularity, and unusual diets require individualized interpretation.
The binary sex coefficient is part of the historical equation and does not represent gender identity. It approximates population differences in creatinine generation and cannot capture the physiology of every person, including transgender, intersex, or gender-diverse patients. A qualified clinician should choose the approach using the patient’s clinical history, hormone exposure, body composition, serial values, and the purpose of estimation.
The displayed threshold is user-entered and has no built-in drug meaning. Some labels use categories such as at least 50, 30–49, 15–29, or below 15; others use different boundaries, contraindications, loading-dose instructions, dialysis timing, or indication-specific adjustments. Use the exact current label rather than memory or a threshold copied from another medication.
Frequently asked questions
Is Cockcroft–Gault the same as eGFR?
No. Cockcroft–Gault estimates creatinine clearance in unindexed mL/min and includes weight. Laboratory CKD-EPI eGFR is usually normalized to 1.73 m² and is derived differently. A label may specify one or be based on older study methods.
Which weight should I choose?
Use the body-weight convention supported by the drug’s prescribing information, clinical evidence, and local pharmacy policy. Actual, ideal, and adjusted weight are all shown because there is no universal choice across body sizes and drugs.
Should low serum creatinine be rounded to 1.0?
This calculator does not round it. Routine rounding can underestimate clearance and lacks universal evidence. Low muscle mass can make creatinine-based estimates unreliable, which calls for clinical evaluation rather than an automatic numerical patch.
Can this calculate a medication dose?
No. It estimates one renal-function input. Dose, interval, maximum, indication, interactions, dialysis status, age limits, and monitoring must come from the current label and qualified prescriber or pharmacist.
Why is height required?
Height is not in the core Cockcroft–Gault equation. It is needed for the optional Devine and adjusted-weight comparisons and for contextual BSA. Actual-weight eCrCl can be calculated without using height as its scalar.
What if creatinine is changing quickly?
Steady-state equations may be misleading in acute kidney injury or recovery. Clinicians use trends, urine output, timing, kinetic approaches, measured methods, drug levels, and the clinical situation.
Related planning context
If medical care is part of a household’s broader U.S. It does not determine medical-expense deductibility or any clinical decision.
References
- Cockcroft and Gault: Prediction of creatinine clearance from serum creatinine
- NIDDK: Determining Drug Dosing in Adults with Chronic Kidney Disease
- FDA: Pharmacokinetics in Patients with Impaired Renal Function
- Brown et al.: Estimating creatinine clearance—a meta-analysis
- Universal equation for estimating ideal body weight and body weight at any BMI
Educational use only. Verify current drug labeling, laboratory methods, and local policy with a licensed pharmacist or prescriber.