# Cockcroft-Gault Calculator

> Cockcroft-Gault estimates creatinine clearance in mL/min as ((140 − age) × weight in kg × 0.85 if female) / (72 × serum creatinine in mg/dL). It is a historical drug-dosing equation, not the NKF-recommended method for staging CKD.

**Last updated:** September 2026
**URL:** https://bodyhealthcalculator.com/cockcroft-gault-calculator
**Category:** Kidney & Filtration

## How it works

CrCl = (140 − age) × chosen weight (kg) / (72 × Scr mg/dL), then × 0.85 if female. Ideal weight uses Devine. Adjusted weight is IBW + 0.4 × (actual − IBW) when actual exceeds IBW.

## What Cockcroft-Gault estimates

Cockcroft-Gault estimates creatinine clearance, not GFR.

Clearance is the volume of plasma cleared of creatinine per minute. Proximal tubules secrete creatinine, so clearance usually sits above true GFR. The 1976 paper predicted 24-hour measured creatinine clearance from serum creatinine, age, and weight in 249 men at a Canadian veterans hospital, then cut the result by about 15% for women.

The formula is CrCl (mL/min) = (140 - age) × weight (kg) / (72 × Scr mg/dL), times 0.85 in females. Output is unindexed mL/min. Older labels still name that unit after labs moved to indexed eGFR. NKF wants adult drug decisions on race-free eGFR scaled to body surface area. FDA 2024 prefers eGFR for new pharmacokinetic studies. Plenty of marketed drugs still list CrCl cutoffs from the Cockcroft-Gault era. Follow the label in front of you when a dose is at stake.

Sources: [1] [2] [3]

## Formula and weight choices

Pick actual body weight, Devine ideal body weight, or adjusted body weight. Devine IBW (kg) is 50 + 2.3 × inches over 60 in men and 45.5 + 2.3 × inches over 60 in women. Adjusted weight is IBW + 0.4 × (actual - IBW) when actual exceeds IBW, otherwise actual.

Cockcroft and Gault used measured weight in a 96% male cohort that does not match today’s obesity pattern. Winter and Brown later compared actual, ideal, and adjusted weight because one descriptor fails at both extremes. There is no universally validated switch. Write down the weight you used.

Rounding a low creatinine up to 0.8 or 1.0 mg/dL in older adults is a local habit. It is not in the 1976 equation. This page does not round. If a protocol requires it, do that step in the protocol.

Sources: [1] [4] [5]

## Worked Cockcroft-Gault examples

A 70-year-old man, 80 kg, creatinine 1.2 mg/dL: (140 - 70) × 80 / (72 × 1.2) = 64.8, shown as 65 mL/min on actual weight.

A 60-year-old woman, 70 kg, creatinine 1.0: (140 - 60) × 70 / 72 × 0.85 = 66 mL/min. The 0.85 factor is the whole female adjustment. It did not come from a large female derivation set. At 160 cm and 95 kg her Devine IBW is about 52 kg and adjusted weight is 52 + 0.4 × (95 - 52) = 69 kg, close to a 70 kg actual-weight run. Severe obesity widens the actual-versus-adjusted gap and can change a dosing bin.

An 80-year-old, 50 kg man, creatinine 0.7: actual-weight Cockcroft-Gault is (140 - 80) × 50 / (72 × 0.7) = 60 mL/min. That sits near a common cutoff while sarcopenia may mean true GFR is lower. Rounding creatinine to 1.0 drops the estimate to 42. This page does not round. If the hospital requires it, write the protocol step down.

*Cockcroft-Gault with actual body weight*

| Person | Weight | Creatinine | Estimated CrCl |
| --- | --- | --- | --- |
| Man, 70 years | 80 kg | 1.2 mg/dL | 65 mL/min |
| Woman, 60 years | 70 kg | 1.0 mg/dL | 66 mL/min |

Sources: [1] [4]

## Drug dosing in 2026 versus 1976

IDMS assays report creatinine about 10 to 12% lower than the methods used when many labels were written. 1976 math on a 2026 creatinine can overestimate clearance versus the original pharmacokinetic studies. NKF wants new decisions on eGFR rather than perpetual Cockcroft-Gault.

FDA 2024 tells new kidney-impairment PK studies to use eGFR. Older labels were not rewritten overnight. Pharmacists still run Cockcroft-Gault when a monograph names it.

KDIGO stages CKD with eGFR and albuminuria. A CrCl of 55 mL/min is not “stage 3.” Stage language belongs with indexed eGFR plus ACR.

*Which kidney number answers which question*

| Question | Preferred metric | This calculator |
| --- | --- | --- |
| CKD staging | 2021 eGFR plus ACR | No |
| Old label with CrCl cutoffs | Cockcroft-Gault (if named) | Yes |
| New PK studies (FDA 2024) | eGFR | No |
| Unusual muscle mass | Cystatin C or measured GFR | No |

Sources: [2] [3] [6]

## How labels still name Cockcroft-Gault

A trial that enrolled people with actual-weight Cockcroft-Gault and then wrote “avoid if CrCl under 30 mL/min” is describing that equation.

Swap in indexed 2021 eGFR of 28 mL/min/1.73 m² for a 110 kg adult and you can withhold a drug whose unindexed clearance is still above 30. Swap in Cockcroft-Gault of 55 mL/min for a 45 kg adult and you can give a full dose when indexed eGFR is 32. Chart the equation name, weight method, creatinine date, and number. A later clinician cannot reconstruct “CrCl 40” without those details. This page shows the weight used so you can copy it.

Sources: [2] [3] [6]

## Inputs you need to measure

Weigh on a calibrated scale.

Edema and ascites add water that does not generate creatinine. Ideal or adjusted weight may sit closer to the muscle the equation expects. That is an approximation, not a correction proven in ascites trials. Height should be current. A standing height from a decade ago distorts Devine IBW. Recumbent length is a different technique. Label it.

Creatinine has to be a laboratory value. Trimethoprim and cimetidine raise creatinine and therefore lower calculated CrCl without a matching drop in true GFR.

Sources: [4] [5]

## Groups in whom the equation is a poor fit

Cirrhosis lowers creatinine generation. Cockcroft-Gault then overestimates clearance, sometimes by a lot, and the extra dose of a renally cleared drug follows.

Prefer measured methods or cystatin-based estimates there. The derivation sample had almost no women. The 0.85 factor is a literature adjustment, not a regression coefficient from female participants. Pregnancy, children, and dialysis sit outside the equation.

Very low creatinine from low muscle can inflate CrCl into a range that looks “normal” while true GFR is reduced. Do not round the result up for comfort. Look at ACR, cystatin C, and the clinical picture.

Sources: [4] [5] [7]

## Limitations and safety

This page does not cap clearance at 120 or 150 mL/min. Some dosing tables do. Apply a protocol cap after you read the uncapped estimate.

The calculator cannot pick a drug, a loading dose, or a dialysis schedule. Narrow-therapeutic-index agents need local pharmacy rules and, when available, drug levels. Aminoglycosides historically used ideal or adjusted weight. Direct oral anticoagulants often list CrCl cutoffs from actual-weight Cockcroft-Gault trials. The wrong weight method can move someone across a 30 or 50 mL/min label line. Copy the method named in the monograph.

If eGFR is 38 mL/min/1.73 m² and Cockcroft-Gault is 61 mL/min, the gap is expected in a large or muscular person: one number is indexed and one is not. Convert eGFR to mL/min with BSA before claiming the tests disagree. If urine output stops, potassium rises, or pulmonary edema appears, equations are irrelevant. Seek emergency care.

Sources: [2] [6] [7]

## FAQ

### Should I still use this for medication dosing?

Many older labels used Cockcroft-Gault. NKF now favors race-free eGFR adjusted to the patient body surface area, and FDA 2024 guidance prefers eGFR for new pharmacokinetic studies. Follow the specific drug label and pharmacist protocol.

### Which weight should I pick?

The 1976 paper used measured weight in a mostly male veteran sample. Later pharmacy practice often uses actual weight if below ideal, and adjusted weight in obesity. Document the choice.

### Why is the unit mL/min instead of mL/min/1.73 m²?

Cockcroft-Gault estimates unindexed clearance. CKD-EPI reports an indexed eGFR. They are not interchangeable without converting for body surface area.

## References

1. Cockcroft and Gault, 1976. [Prediction of creatinine clearance from serum creatinine](https://pubmed.ncbi.nlm.nih.gov/1244564/)
2. National Kidney Foundation. [Cockcroft-Gault Equation for Estimating Creatinine Clearance](https://www.kidney.org/professionals/kdoqi/cockcroft-gault-equation-estimating-creatinine-clearance)
3. FDA, 2024. [Pharmacokinetics in Patients with Impaired Renal Function (guidance for industry)](https://www.fda.gov/regulatory-information/search-fda-guidance-documents/pharmacokinetics-patients-impaired-renal-function-study-design-data-analysis-and-impact-dosing)
4. Winter et al., 2012. [Impact of body weights on Cockcroft-Gault accuracy](https://pubmed.ncbi.nlm.nih.gov/22576791/)
5. Brown et al., 2013. [Which weight to use in Cockcroft-Gault](https://pubmed.ncbi.nlm.nih.gov/23757387/)
6. KDIGO. [KDIGO 2024 CKD Guideline](https://kdigo.org/guidelines/ckd-evaluation-and-management/)
7. Lam et al.. [Cockcroft-Gault in cirrhosis](https://pmc.ncbi.nlm.nih.gov/articles/PMC5295146/)

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