Source says
eGFR / CKD-EPI
Use the eGFR pathway
Common laboratory form: mL/min/1.73 m². Follow the exact form and units required by the source.
Renal function for medication decisions
Renal Function Calculators
The difficult part is often not the arithmetic. It is knowing which renal estimate the current medicine or clinical source is asking for. Start with the method name and units, then calculate that exact estimate.
Source names the method
Units stay attached
Trend and context matter
Method decision
Do you need eGFR or creatinine clearance?
Source says
CrCl / Cockcroft-Gault
Use the CrCl pathway
Reported as mL/min and includes a selected body weight. The source should govern the weight method.
If the source only says “renal function”: do not guess which estimate it means when the choice could affect a medication decision. Check the medicine-specific or local source.
Calculate now
Choose the estimate named by your source
The two renal calculators stay separate because eGFR and Cockcroft-Gault CrCl are not interchangeable names for the same calculation.
mL/min/1.73 m²
CKD-EPI 2021
→ eGFR
Calculate adult CKD-EPI 2021 eGFR from creatinine, with optional cystatin C and BSA adjustment where the workflow requires it.
Use when: The source asks for eGFR, CKD-EPI, or a value in mL/min/1.73 m².
Calculate eGFRmL/min
Cockcroft-Gault
→ CrCl
Calculate adult Cockcroft-Gault creatinine clearance using age, serum creatinine and the body-weight method required by the current source.
Use when: The source explicitly asks for CrCl or Cockcroft-Gault in mL/min.
Calculate CrClSupporting calculation
Need an explicitly specified IBW or adjusted body weight for Cockcroft-Gault?
Use the Dosing Body Measures hub only after the governing source has told you which body-weight method is required.
A renal estimate is not a medication dose
MedMaths calculates the renal estimate you select. It does not choose a medicine, dose, interval, renal threshold, contraindication or dialysis adjustment. Use the current medicine-specific source after calculating the estimate it requires.
Understand
Understand the estimate before relying on the number
Use these Guides when the difficult part is method choice, Cockcroft-Gault weight selection, or understanding why two renal estimates do not match.
Method choice
eGFR vs CrCl: which renal function estimate should you use?
Compare CKD-EPI eGFR with Cockcroft-Gault CrCl, why the values differ, and how to follow the estimate and units required by the current source.
Read GuideFormula explainer
The Cockcroft-Gault equation explained
Understand what Cockcroft-Gault calculates, why the selected body weight changes CrCl, and the main limitations of the estimate.
Read GuideWeight-method support
Ideal vs adjusted body weight for medication dosing
Understand IBW and AdjBW before using either value in a Cockcroft-Gault workflow that explicitly requires that weight method.
Read GuideBefore you calculate
Four checks that prevent method errors
Read the method name
Look for eGFR / CKD-EPI or CrCl / Cockcroft-Gault in the governing source.
Check the units
Keep mL/min/1.73 m² and mL/min visible. They are not decorative labels.
For CrCl, verify the weight method
Do not let actual, ideal or adjusted weight be selected automatically if the source specifies one.
Review trend and limitations
A single creatinine-based estimate may be less reliable when renal function is changing rapidly or creatinine generation is unusual.
What the numbers mean
Keep method, value and unit together
Example label
CKD-EPI 2021 eGFR
62 mL/min/1.73 m²
Different label
Cockcroft-Gault CrCl
54 mL/min
These example values are shown only to demonstrate why a renal result should retain its method name and units. They are not a dosing recommendation or expected conversion.
Common renal-calculation mistakes
The method error can matter more than the arithmetic error
Treating eGFR and CrCl as the same value
They are different estimates built from different equations. Match the method and units to the current source rather than swapping one number for the other.
Ignoring indexed versus absolute units
Laboratory eGFR is commonly reported as mL/min/1.73 m², while Cockcroft-Gault CrCl is reported as mL/min. The unit is part of the answer.
Letting the calculator choose a CrCl weight
Actual, ideal and adjusted body weight can change Cockcroft-Gault CrCl. Use the body-weight method specified by the governing source.
Over-trusting one creatinine result
Creatinine-based estimates can be less reliable when renal function is changing rapidly or creatinine does not reflect filtration well. Review the clinical context and trend.
Used in clinical areas
See renal estimates alongside the other calculations and clinical context commonly grouped in these specialties.
Related calculation topics
Continue when the renal estimate connects to a body-weight method, laboratory calculation or medication-dose calculation.
Renal function calculator FAQs
Answers about choosing eGFR or Cockcroft-Gault CrCl without turning the topic hub into a medication-dosing protocol.
Renal function calculator FAQs
Answers about choosing eGFR or Cockcroft-Gault CrCl without turning the topic hub into a medication-dosing protocol.
Should I use eGFR or creatinine clearance for medication dosing?
Use the renal estimate and units specified by the current medicine reference, product information, pharmacist, prescriber instruction, or local protocol.
- If the source names Cockcroft-Gault or CrCl, use the creatinine-clearance calculator.
- If the source names CKD-EPI or eGFR, use the eGFR calculator in the required form and units.
- If the source is unclear and the choice could change a medication decision, verify the required method rather than choosing from memory.
Why can eGFR and Cockcroft-Gault CrCl give different numbers?
They are different estimating equations and handle body size differently, so their numerical results are not expected to match exactly.
- CKD-EPI eGFR is commonly indexed to a standard body surface area of 1.73 m².
- Cockcroft-Gault directly includes a selected body weight and reports an absolute mL/min estimate.
- The estimates were developed for different purposes and populations.
Does an eGFR in mL/min become the same as Cockcroft-Gault CrCl?
No. De-indexing eGFR can express an eGFR-based estimate in mL/min, but it does not turn CKD-EPI into Cockcroft-Gault creatinine clearance.
- The underlying equations remain different.
- Always keep the method name attached to the numerical result when a threshold or medication decision depends on it.
Can MedMaths choose a renal medication dose or dosing interval?
No. MedMaths calculates the selected renal estimate; it does not choose a medicine, dose, interval, contraindication threshold, or dialysis adjustment.
- Medication actions are product- and context-specific.
- Use the current medicine-specific source after calculating the renal estimate it requires.
What should I check before calculating Cockcroft-Gault CrCl?
Confirm age, serum-creatinine unit, sex factor, and the body-weight method required by the source before calculating.
- A µmol/L value entered into an mg/dL equation can create a major error.
- Different body-weight methods can move the result across a medicine-specific threshold.
Formula origins in this topic
The equations used in these calculators were developed by published researchers. These researchers are not affiliated with MedMaths and have not reviewed or endorsed this site.
Cockcroft-Gault Equation
Formula originally described by: Donald W. Cockcroft and M. Henry Gault
CKD-EPI 2021 Creatinine and Creatinine-Cystatin C Equations — CKD-EPI Collaboration
Based on research published by: Lesley A. Inker and Andrew S. Levey
References
Primary equation papers and current kidney-function guidance supporting the distinction between CKD-EPI eGFR and Cockcroft-Gault CrCl.
References
Primary equation papers and current kidney-function guidance supporting the distinction between CKD-EPI eGFR and Cockcroft-Gault CrCl.
Prediction of creatinine clearance from serum creatinine
Cockcroft & Gault, Nephron (1976)
Original publication of the Cockcroft-Gault creatinine-clearance equation.
New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race
New England Journal of Medicine (2021)
Primary 2021 CKD-EPI publication for the contemporary race-free adult eGFR equations.
Determining Drug Dosing in Adults with Chronic Kidney Disease
NIDDK
Clinical guidance on kidney-function estimates, body-size indexing and medication-dosing decisions.
KDIGO 2024 CKD Guideline
KDIGO
Current international guidance for evaluation and management of chronic kidney disease, including GFR assessment.