What is the Cockcroft-Gault equation?

Cockcroft-Gault (published in Nephron, 1976) estimates creatinine clearance as CrCl = ((140 - age) x weight x F) / (72 x serum creatinine), where F = 1.0 for males and 0.85 for females, weight is in kg and serum creatinine is in mg/dL. It remains the reference formula for most drug-dosing adjustments in renal impairment despite the existence of newer GFR estimating equations.

Should I use actual weight, IBW or ABW?

When actual body weight is less than ideal body weight (IBW), use actual weight. When actual weight exceeds IBW, most guidelines recommend IBW to avoid overestimating clearance. In obesity (actual weight more than 130% of IBW), adjusted body weight (ABW = IBW + 0.4 x (actual - IBW)) is preferred by many institutions. Always follow your local pharmacy or clinical protocol.

How is ideal body weight calculated?

The Devine formula is used: IBW (male) = 50 kg + 2.3 x (height in inches - 60); IBW (female) = 45.5 kg + 2.3 x (height in inches - 60). Height in centimetres is divided by 2.54 to convert to inches. A floor of the base weight (50 or 45.5 kg) is applied for patients shorter than 5 feet (152.4 cm).

How do I convert creatinine from µmol/L to mg/dL?

Divide by 88.42. So 100 µmol/L = 100 / 88.42 = 1.131 mg/dL. The conversion factor comes from the molecular weight of creatinine (113.12 g/mol). This tool performs the conversion automatically when you select µmol/L.

What is the difference between CrCl and eGFR?

Creatinine clearance (CrCl) is an estimate of the rate at which the kidneys filter creatinine, expressed in mL/min. eGFR (estimated glomerular filtration rate), typically calculated by the CKD-EPI 2021 equation, is normalised to a body surface area of 1.73 m² and expressed as mL/min/1.73 m². CrCl from Cockcroft-Gault is the preferred input for most drug-dosing decisions; eGFR is preferred for CKD staging and epidemiology.

Is this calculator suitable for clinical use?

This tool is provided for educational and reference purposes only. It should never replace the judgement of a qualified clinician or registered pharmacist. Drug dosing in renal impairment depends on many factors beyond CrCl, including the drug's therapeutic index, protein binding, and the patient's clinical status. Always verify with your institution's dosing guidelines or a clinical pharmacist.

Creatinine Clearance Calculator (Cockcroft-Gault)

Kidney function declines with age, disease and medications, and the rate of decline directly determines how the body handles drugs that are cleared renally. The Cockcroft-Gault creatinine clearance is the single most widely used estimate of kidney function for drug dosing adjustments, appearing in almost every drug summary of product characteristics (SPC) and prescribing reference for renally-cleared medications — from aminoglycosides and vancomycin to metformin and low-molecular-weight heparin.

This calculator implements the original 1976 equation exactly, supports both mg/dL and µmol/L creatinine inputs, calculates ideal body weight (IBW) using the Devine formula and adjusted body weight (ABW) for obese patients, and maps the result to the KDIGO 2012 CKD staging framework. Everything runs in your browser — no data leaves your device.

How it works

The Cockcroft-Gault (CG) formula published in Nephron 1976 is:

CrCl = ((140 - age) x weight x F) / (72 x SCr)

where age is in years, weight is in kg, SCr is serum creatinine in mg/dL and F is the sex factor (1.0 for males, 0.85 for females). The 0.85 factor reflects the lower muscle mass — and therefore lower creatinine production — in females.

If creatinine is reported in µmol/L (standard in the UK and Europe) the tool converts it first: mg/dL = µmol/L / 88.42, using the molecular weight of creatinine (113.12 g/mol).

Ideal body weight (IBW) is calculated using the Devine formula:

Male: IBW = 50 + 2.3 x (height_inches - 60)
Female: IBW = 45.5 + 2.3 x (height_inches - 60)

When actual weight exceeds IBW, the standard recommendation is to use IBW in the CG formula to avoid over-estimating clearance in overweight patients. In obesity (actual weight more than 130% of IBW), adjusted body weight corrects for lean-mass differences: ABW = IBW + 0.4 x (actual_weight - IBW).

CKD staging follows KDIGO 2012: G1 (>=90 mL/min), G2 (60-89), G3a (45-59), G3b (30-44), G4 (15-29), G5 (<15).

Worked example

A 68-year-old female patient, weighing 72 kg, height 162 cm, with a serum creatinine of 1.4 mg/dL:

IBW = 45.5 + 2.3 x (162/2.54 - 60) = 45.5 + 2.3 x (63.78 - 60) = 45.5 + 8.7 = 54.2 kg
Actual weight (72 kg) exceeds IBW (54.2 kg), so use IBW.
CrCl = ((140 - 68) x 54.2 x 0.85) / (72 x 1.4)
CrCl = (72 x 54.2 x 0.85) / 100.8
CrCl = 3316.6 / 100.8 = 32.9 mL/min

This places her in CKD Stage G3b (moderately to severely decreased kidney function, 30-44 mL/min), which triggers dose reduction or avoidance for many medications.

Age	Sex	Weight	Height	SCr	CrCl (IBW)
45	M	80 kg	180 cm	1.0 mg/dL	95 mL/min
68	F	72 kg	162 cm	1.4 mg/dL	33 mL/min
75	M	70 kg	170 cm	1.8 mg/dL	34 mL/min
55	F	95 kg	165 cm	0.9 mg/dL	71 mL/min

Note: This calculator is for educational purposes only. Always confirm drug-dosing decisions with a qualified clinician or pharmacist.