Creatinine Clearance Calculator
The Cockcroft–Gault estimate — age, weight, serum creatinine and sex into the mL/min figure drug labels still dose by.
Creatinine Clearance Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Steady-state patients only
- Actual-weight arithmetic; no IBW/ABW switch
In short: A 65-year-old man at 70 kg with a serum creatinine of 1.2 mg/dL clears an estimated 60.763889 mL/min — (140 − 65) × 70 ÷ (72 × 1.2). The same patient female reads 51.649306, the 0.85 muscle-mass correction doing exactly what it says. Both sit in the moderate-decrease band, which for drug dosing is the region where labels start adjusting — and the 72 in the denominator is not mysticism, it is the unit conversion that turns the raw quotient into mL/min.
Formula
CrCl = (140 − age) × kg ÷ (72 × SCr) ··· × 0.85 female
Cockcroft–Gault (1976) reads creatinine production off age, weight and sex, then divides by what the blood shows: production over concentration is clearance. The 72 converts units to mL/min. The 0.85 for women prices lower average muscle mass per kilogram — a population correction, not a property of the patient in front of you.
Worked Example
- Enter age, weight and serum creatinine.
- Set sex for the 0.85 correction.
- Read the mL/min estimate and its band.
- Check the drug’s dosing table against this figure.
Defaults: 65 M, 70 kg, SCr 1.2 → 60.763889 mL/min. Female on the same labs → 51.649306. A 40-year-old at 0.9 clears 108.641975 — the young-kidney end of the band.
Strengths & Limits Of This Model
Where this engine is strong
- Both sexes priced, correction visible
- Band card speaks orientation, not verdict
Where it stops
- No cystatin-C or eGFR paths
- No pediatric form
Practical Use Cases
Drug dosing
the label’s own renal table
Nephrology triage
a number before the scan
Teaching
production over concentration
Methodology & Editorial Standards
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Creatinine Clearance Calculator — 8 Expert FAQs
8 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
Why does the drug label say Cockcroft–Gault when the lab reports eGFR?
Because the trials that set the doses ran on Cockcroft–Gault, and labels change slowly. The two estimates answer different questions: eGFR is the diagnostic — indexed to body surface area, stage-graded — while CG is unindexed mL/min, which is what dose tables are written against. Using the diagnostic number where the label expects the dosing number is a known source of under-dosing in small patients.
Which weight do I enter?
The protocol’s choice: actual body weight for most non-obese patients, ideal or adjusted weight when the protocol says so — fat does not make creatinine, so actual weight in obesity over-estimates clearance. The page multiplies whatever body it is given and says so; the weight policy lives on the order.
What is the 0.85 doing for women?
Pricing population muscle mass: women average lower creatinine production per kilogram, so the same serum value implies less clearance. It is a population patch on a population formula — a muscular woman and a slight man bracket it. The card prints both the corrected and the raw figure so the correction is never invisible.
My patient’s creatinine is changing fast.
Then no estimate is safe — Cockcroft–Gault assumes a steady state, production balanced by clearance. Acute kidney injury breaks the assumption: the serum value lags the injury, and the formula will confidently print a clearance the patient does not have. Estimates are for stable patients; changing ones need the team.
How accurate is the estimate?
Broad but not sharp — it was built on a small 1976 cohort of men and behaves worst at extremes of age, weight and muscle. That is why the band card speaks in orientation bands rather than verdicts, and why dosing decisions quote the number with its assumptions. It remains the label standard because the labels were written with it.
What weight do I enter for an obese patient?
Whichever the protocol names — actual, ideal (the Devine formulas), or adjusted — the ideal plus four-tenths of the excess. Fat produces little creatinine, so actual weight in obesity inflates the estimate and the dose with it. This page multiplies the kilograms it is given; the weight policy is a chart decision that should be quoted next to the number.
Does the formula still work after amputation?
Only with an adjusted weight — the numerator assumes the whole body is producing creatinine. Describing-weight conventions exist for exactly this, and the estimate inherits their roughness. In any body far from the original cohort, treat the output as a starting point for the pharmacist, not the last word.
Why 72, of all numbers?
Unit conversion — it folds the concentration and time-unit factors into one constant so the answer lands in mL/min. It is not physiology; patients cleared creatinine perfectly well before it was chosen, and no one has ever divided by it at the bedside twice.