GFR Calculator
Estimate your glomerular filtration rate (eGFR) from serum creatinine, age and sex using the 2021 CKD-EPI equation, which does not use race, and see the kidney function stage and Cockcroft-Gault creatinine clearance. Example: a 50-year-old woman with a creatinine of 0.9 mg/dL has an eGFR of about 78 mL/min/1.73 m2.
Show steps
How to use the GFR Calculator
- Enter your serum creatinine from a blood test and choose the unit.
- Enter your age and sex at birth; add weight to also see Cockcroft-Gault.
- Press Calculate to see the eGFR and kidney function stage.
Formula and method
CKD-EPI 2021: eGFR = 142 x min(Scr/k, 1)^a x max(Scr/k, 1)^-1.200 x 0.9938^age x 1.012 (if female), where k = 0.7 (female) or 0.9 (male) and a = -0.241 (female) or -0.302 (male). Cockcroft-Gault: CrCl = (140 – age) x weight / (72 x Scr), times 0.85 if female.
Worked example: woman, 50, creatinine 0.9 mg/dL
| Step | Value |
|---|---|
| Scr / 0.7 | 1.286 |
| max(…)^-1.2 | 0.740 |
| 0.9938^50 | 0.733 |
| 142 x 0.740 x 0.733 x 1.012 | 78 mL/min/1.73 m2 |
Kidney function stages (G categories)
| Stage | eGFR | Description |
|---|---|---|
| G1 | 90 or above | Normal or high |
| G2 | 60 to 89 | Mildly decreased |
| G3a | 45 to 59 | Mild to moderately decreased |
| G3b | 30 to 44 | Moderately to severely decreased |
| G4 | 15 to 29 | Severely decreased |
| G5 | Below 15 | Kidney failure |
eGFR versus creatinine clearance
eGFR is standardized to body surface area and used to stage kidney disease. Cockcroft-Gault gives clearance in mL/min and is still used by many drug labels for dose adjustment.
Why age lowers eGFR
Kidney filtration declines gradually with age, so the same creatinine gives a lower eGFR in an older adult.
Frequently asked questions
What is a normal GFR?
About 90 or higher for a healthy young adult, declining with age.
What is the CKD-EPI 2021 equation?
The current standard that estimates GFR from creatinine, age and sex without a race coefficient.
What eGFR means kidney disease?
Below 60 for 3 months or more, or kidney damage markers at any eGFR.
How do I convert creatinine units?
Divide umol/L by 88.4 to get mg/dL.
Can eGFR be wrong?
Yes, in very muscular or frail people, pregnancy and acute illness.
What should I do about a low result?
Ask your clinician about repeat testing and a urine albumin test.
Sources
- National Kidney Foundation: eGFR calculator
- Inker et al., NEJM 2021: New creatinine- and cystatin C-based equations
Related calculators
Related to This Article
More math articles
- Deviance, Crime, Harm, and Social Definition
- Lines of Symmetry for 4th Grade
- Culture
- Using a Comparison Matrix
- 8th Grade IAR Math Practice Test Questions
- RD Exam Content Outline Changes: Rebuild Your Study Plan (2027 Prep)
- The Ultimate 6th Grade LEAP Math Course (+FREE Worksheets)
- Disasters and Collective Response
- Math Word Problem Generator
- Appellate jurisdiction
What people say about "GFR Calculator: eGFR by CKD-EPI 2021 with Kidney Stage"?
No one replied yet.