Creatinine Clearance Calculator (Cockcroft-Gault)
Estimate creatinine clearance with the Cockcroft-Gault equation and check renal drug-dosing thresholds.
검사 결과가 µmol/L 단위면 88.4로 나눠 mg/dL로 변환해 입력하세요. (예: 88 µmol/L ≒ 1.0 mg/dL)
Cockcroft-Gault 공식 · 실제체중 70kg 적용
계산 과정
CrCl 구간별 신기능 (mL/min)
약물 용량 조절 참고
대부분의 약물에서 일반 용량을 사용합니다. (CrCl 50 이상)
결과 공유
의료 주의사항
- 이 계산기는 참고용이며 의료진의 처방·판단을 대체할 수 없습니다. 계산값만 보고 약을 임의로 감량하거나 중단하지 마세요.
- Cockcroft-Gault는 1973년 공식으로, 체표면적 보정이 없는 실측 단위(mL/min)라 약물 용량 조절(신배설 약물의 감량·금기 기준)에 널리 쓰입니다. 만성콩팥병 단계 진단은 CKD-EPI 2021 기반 eGFR(mL/min/1.73㎡)을 사용합니다.
- 18세 이상 성인용입니다. 급성 신손상처럼 크레아티닌이 빠르게 변하는 상황, 임신, 사지절단·근감소증·보디빌더 등 근육량이 극단적인 경우에는 오차가 큽니다.
- CrCl이 60 미만이거나 이전 검사보다 크게 떨어졌다면 신장내과 진료를 받으세요.
Overview
Creatinine clearance (CrCl) estimates how many milliliters of blood the kidneys clear of creatinine each minute, and the Cockcroft-Gault equation published in 1973 derives it from age, weight, sex, and serum creatinine alone. Unlike eGFR, which is normalized to a body surface area of 1.73 m², CrCl is reported in un-indexed mL/min, which is why it remains the standard input for adjusting doses of renally cleared drugs. Many product labels — DOACs, several antibiotics, metformin and others — define their reduction and contraindication thresholds against Cockcroft-Gault CrCl rather than CKD stage. This calculator also derives Devine ideal body weight and adjusted body weight so that obesity does not silently inflate the result, a common bedside error.
Formula
CrCl (mL/min) = ((140 − age) × weight in kg) ÷ (72 × serum creatinine in mg/dL), multiplied by 0.85 for women | Ideal body weight (Devine) = 50 + 2.3 × (height in inches − 60) for men, 45.5 + 2.3 × (height in inches − 60) for women | Adjusted body weight = IBW + 0.4 × (actual weight − IBW), recommended when actual weight exceeds 130% of IBW | Example: a 60-year-old man, 70 kg, creatinine 1.0 → (140 − 60) × 70 ÷ (72 × 1.0) = 5,600 ÷ 72 ≈ 77.8 mL/min
How to Use
- 1Select sex. The 0.85 factor for women is applied automatically to reflect lower muscle mass.
- 2Enter age in years and serum creatinine in mg/dL. If your lab reports µmol/L, divide by 88.4 first.
- 3Enter weight in kg and height in cm; height drives the Devine ideal and adjusted body weights.
- 4Leave the weight basis on 'auto' to switch to adjusted body weight only when actual weight exceeds 130% of ideal.
- 5Read the CrCl value, its renal-function band, and the drug-dosing thresholds at 50 and 30 mL/min.
Examples
60-year-old man, 70 kg and 170 cm, creatinine 1.0 mg/dL
An average-build middle-aged man whose screening creatinine came back normal.
75-year-old woman, 52 kg and 158 cm, creatinine 1.3 mg/dL
Advanced age plus low body weight pushes clearance far lower than the creatinine value suggests.
45-year-old man, 110 kg and 175 cm, creatinine 1.1 mg/dL (obese)
The textbook case for not entering actual body weight.
Background
The Cockcroft-Gault equation comes from a 1973 Nephron paper that regressed 24-hour urine creatinine clearance in 249 patients, most of them men; the 72 in the denominator and the 0.85 female factor are empirical constants from that dataset, not derived quantities. Age sits in the numerator because muscle mass, and therefore creatinine production, falls with age — so the same creatinine value implies worse kidney function in an older patient. The National Kidney Foundation and KDIGO recommend the 2021 CKD-EPI eGFR for staging chronic kidney disease, yet most drug labels were written against Cockcroft-Gault CrCl, so clinical pharmacy practice keeps both and picks by purpose. In obesity, actual body weight inflates the result because adipose tissue contributes almost no creatinine while still entering the numerator, which is why an adjusted body weight with a 40% correction factor is the widely used convention once actual weight passes 130% of ideal.
Tips
- ✔Check the lab units first — entering a µmol/L value directly makes CrCl come out roughly 88 times too low.
- ✔In older or low-muscle-mass patients a 'normal' creatinine can still mean a low clearance. Judge from CrCl, not the raw value.
- ✔No estimating equation is valid in acute kidney injury while creatinine is still moving. Use a stable value.
- ✔When a drug label specifies 'creatinine clearance', it means this Cockcroft-Gault figure, not eGFR.
- ✔Recalculate after any significant weight change — weight enters the result proportionally.
- ✔This is a reference tool. Any dose reduction or discontinuation should be decided with the prescriber or pharmacist.
FAQ
Q. My eGFR calculator gives a different number — which is right?
Both are correct; the units differ. eGFR is indexed to 1.73 m² of body surface area (mL/min/1.73 m²) while CrCl is un-indexed (mL/min), so larger people get a higher CrCl than eGFR and smaller people a lower one. CKD staging (G1–G5) uses eGFR; renal drug dose adjustment conventionally uses CrCl.
Q. Should I use actual, ideal, or adjusted body weight?
Use actual weight when it is at or below 130% of ideal. Above that, adjusted body weight is recommended, which is what the 'auto' setting applies. If the patient weighs less than ideal body weight, use actual weight. Some drugs and institutional protocols mandate ideal body weight instead, so the basis can also be selected manually.
Q. At what CrCl do drugs need reducing?
It varies by drug, but 50 and 30 mL/min are the thresholds seen most often. Above 50, standard dosing usually applies; 30–49 triggers reduction for many agents; below 30 the reductions grow larger and some drugs become contraindicated. Below 15 is the range where renal replacement therapy is considered. Always follow the specific label and clinical judgement.
Q. My creatinine is normal but CrCl is under 60 — how?
That is common in older or lighter patients. Creatinine is produced by muscle, so with little muscle mass the value stays low even as filtration falls. Because CrCl folds in age and weight, it exposes the reduced function that a 'normal' creatinine hides. If it is reproducible, a nephrology referral is reasonable.
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