Creatinine Clearance Calculator
Estimate creatinine clearance by Cockcroft-Gault — the measure most drug labels actually specify for renal dose adjustment.
Creatinine Clearance Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Assumes steady-state creatinine; invalid in acute kidney injury or rapidly changing function.
- Unreliable at extremes of muscle mass, in amputation, pregnancy and on dialysis.
- Derived in 1973 from 249 men; the female factor is an approximation.
In short: An 82-year-old woman of 52 kg with a serum creatinine of 1.0 mg/dL has a Cockcroft-Gault creatinine clearance of 35.6 mL/min, against a lab-reported eGFR of 56.2. That 20.6 mL/min gap flips the dosing decision at two common thresholds — which is why the label's chosen measure matters.
Formula
CrCl is absolute mL/min. eGFR is indexed to 1.73 m². Different quantities, different units.
Worked Example
- Take the age term. 140 − 82 = 58.
- Scale by weight. 58 × 52 kg = 3,016.
- Divide by creatinine. 3,016 ÷ (72 × 1.0) = 41.9 mL/min.
- Apply the female factor. 41.9 × 0.85 = 35.6 mL/min.
- Compare with the lab. CKD-EPI 2021 reports 56.2 — a 20.6 mL/min gap that crosses two dosing thresholds.
This anchor was chosen because it is the case clinicians warn about: an elderly, light patient whose laboratory eGFR looks reassuring while her actual clearance is a third lower. At 35.6 mL/min she sits below the 45 mL/min caution line and below the 50 mL/min reduction line used by several anticoagulants; at 56.2 she clears both. Two of the three available numbers — Cockcroft-Gault and the de-indexed eGFR of 49.1 — say reduce, and the one printed on the lab report says do not. The resolution is not to average them or prefer the newer equation, but to read which measure the drug's own label specifies, because that is the measure its dosing study used.
Strengths & Limits Of This Model
Where this engine is strong
- Reports the measure most drug labels actually specify.
- Shows where CrCl and eGFR fall on opposite sides of a dosing threshold.
- States which body weight is conventional at this patient's habitus.
Where it stops
- Cannot tell you what dose any specific drug requires.
- Cannot detect acute kidney injury or non-steady-state creatinine.
Practical Use Cases
Checking a renally cleared medicine
If the label says CrCl, this is the number it means, not the eGFR on the lab report.
Elderly or low-weight patients
This is where the two measures diverge most, and where the eGFR flatters kidney function.
Reconciling a lab report with a label
De-index the eGFR to mL/min before comparing. See the GFR Calculator.
Understanding a dose that was reduced
A prescriber may be working from a clearance well below the eGFR you were told.
Methodology & Editorial Standards
Creatinine clearance is estimated using the Cockcroft-Gault equation, which combines age, body weight, sex and serum creatinine to produce an absolute clearance in millilitres per minute. The equation was derived in 1973 from a cohort of 249 men, with the female correction applied as a flat 0.85 multiplier rather than a separately fitted coefficient, and it predates the standardisation of creatinine assays. It nonetheless remains the reference measure for renal dose adjustment because the overwhelming majority of existing drug labels defined their thresholds using it, and a threshold means the measure it was derived from. The engine reports the CKD-EPI 2021 estimate alongside for comparison and de-indexes it by body surface area, since the laboratory value is normalised to 1.73 square metres and is therefore not directly comparable to an absolute clearance. Where the two measures fall on opposite sides of a common threshold the engine says so explicitly, because that discordance is the practically important output rather than either figure alone. Ideal and adjusted body weights are reported using the Devine formula, with guidance on which weight is conventional at the patient's body habitus, as using actual weight in obesity overstates clearance. All estimating equations assume steady-state creatinine and are unreliable in acute kidney injury. This calculator is an educational estimate and is not medical advice, diagnosis, treatment or a prescription. It performs arithmetic on values you enter and cannot assess your clinical condition. Never start, stop, change or skip a dose of any medicine on the basis of a number produced here. Dose selection belongs to a prescriber working from the approved product label, your full medication list and your current clinical state. If you are acutely unwell, dehydrated, vomiting, or your kidney function is changing, estimating equations are unreliable and urgent clinical review is required. The engine implements the standard published formula for this calculation. Inputs are validated for domain and sign before evaluation, and any undefined case returns an em-dash rather than a spurious value.
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 — 20 Expert FAQs
20 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
What is the Cockcroft-Gault formula?
CrCl = (140 − age) × weight in kg ÷ (72 × serum creatinine), multiplied by 0.85 for females.
Why does this differ from my eGFR?
They are different quantities. CrCl is absolute mL/min; eGFR is indexed to 1.73 m² of body surface area.
Which should be used for drug dosing?
Whichever the drug's label specifies. About 90% of existing labels define renal cut-offs using CrCl.
Can I use eGFR instead of CrCl?
Not interchangeably. In elderly or low-weight patients the two can differ by 15 to 30 mL/min and cross a threshold.
Which weight should I enter?
Actual weight normally. Above about 30% over ideal body weight, adjusted body weight is the convention.
Why does obesity overstate clearance?
Because fat tissue does not clear creatinine, so actual weight inflates the numerator without any real filtration behind it.
Is it valid in acute kidney injury?
No. It assumes steady-state creatinine. In AKI the estimate lags reality and can lead to overdosing.
Is it valid for children?
No. This equation is for adults. Paediatric renal function uses different equations entirely.
Why is the female factor 0.85?
It approximates lower muscle mass. It was an assumption in the original 1973 work, not a fitted coefficient.
How accurate is a single creatinine?
Not very. A swing of 0.1 mg/dL within normal assay variation can move clearance by several mL/min.
What is de-indexing?
Multiplying eGFR by your BSA and dividing by 1.73, converting it to absolute mL/min for comparison.
Does muscle mass affect this?
Strongly. Creatinine comes from muscle, so a very muscular or very wasted person is poorly estimated.
Does this apply on dialysis?
No. Estimating equations are not valid in dialysis; dosing follows the dialysis modality and schedule.
What is a normal creatinine clearance?
Roughly 90 mL/min or above in a healthy adult, declining by about 1 mL/min per year after 40.
Should I change my medication based on this?
No. Never adjust medication from a calculator. This is arithmetic, not a prescription.
Why is an old formula still used?
Because drug labels encode its thresholds. FDA 2024 guidance prefers eGFR for new studies, so the field is mid-transition.
Is this creatinine clearance calculator free to use?
Yes. It is free, requires no account, and has no usage limits. ApexConverter is funded by contextual advertising, never by selling user data.
Is my data sent to a server?
No. The engine runs as Vanilla JavaScript inside your browser under our Zero-Server Client-Side Execution model. Your figures are computed locally and are never transmitted, logged, or stored.
How accurate is this calculator?
It applies the standard closed-form formula in IEEE-754 double precision, rounding only at the display layer. The engine is reconciled against an independent reference implementation before release.
Does it work on mobile?
Yes. The interface is mobile-first with numeric keypad hints and is tested down to a 320-pixel viewport with no horizontal scrolling.