GFR Calculator
Want to check kidney function estimates? Enter creatinine, age, sex, and height and you will get eGFR from the standard formulas. It is for information only, not a diagnosis.
TL;DR
- Direct GFR measurement is complex, so clinics estimate it from creatinine, age, sex, and height.
- CKD-EPI 2021 (Race-Free) Equation: eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^-1.2 × 0.9938^Age × [1.012 if female]
- Adult CKD-EPI calculation — Input: Serum Creatinine = 1.2 mg/dL, Age = 45 years, Male
How it works
Direct GFR measurement is complex, so clinics estimate it from creatinine, age, sex, and height.
The math
Each formula fits a use: CKD-EPI for screening, MDRD for established disease, Cockcroft-Gault for dosing, Schwartz for kids.
Where κ is 0.7 for females and 0.9 for males, and α is -0.241 for females and -0.302 for males.
Understanding your eGFR: stages & CKD-EPI vs MDRD
eGFR isn’t a grade, it’s a creatinine-based estimate filtered by age/sex. 90+ is normal but needs proteinuria context; 60–89 mild (often age), 45–59 moderate, 30–44 moderate to severe, 15–29 severe, <15 failure. CKD-EPI 2021 (race-free) is current standard, MDRD overcalls at high values, Cockcroft-Gault leans on lean mass and drifts in obesity. That’s why we ask for creatinine in mg/dL + exact age — the rest is interpolation. A stable 58 with no proteinuria generally calls for monitoring, not panic.
| Stage | eGFR (mL/min/1.73m²) | Meaning |
|---|---|---|
| G1 | ≥90 | Normal/high (check proteinuria) |
| G2 | 60–89 | Mild decrease |
| G3a | 45–59 | Moderate |
| G3b | 30–44 | Moderate to severe |
| G4 | 15–29 | Severe |
| G5 | <15 | Failure |
Sources: KDIGO 2024, NIDDK CKD-EPI 2021, NKF. Sources verified — not a diagnosis, discuss labs with your GP.
Examples
Adult CKD-EPI calculation
- Input: Serum Creatinine = 1.2 mg/dL, Age = 45 years, Male
- Kappa = 0.9, Scr/Kappa = 1.33
- Apply CKD-EPI polynomial components
- Result: eGFR = 76.0 mL/min/1.73m² (Stage G2: Mildly decreased)
When to use it
✦ Chronic Kidney Disease Screening
Detect early stages of renal function decline during routine metabolic panels.
✦ Medication Dosage Adjustment
Drugs cleared by the kidneys are dosed safely based on GFR and Cockcroft-Gault clearance.
✦ Pediatric Growth & Renal Monitoring
Use Bedside Schwartz formula to monitor kidney function in children based on height and creatinine.
⚠ Common mistakes
- Important Medical Notice: This calculator is provided strictly for educational and informational purposes. The calculated results are indicative estimates and do not replace professional medical diagnosis, laboratory tests, or specialist nephrological consultation.
- Serum creatinine levels depend on muscle mass, physical activity, meat intake, and hydration status. GFR estimators are screening tools and do not replace professional nephrological evaluation.
FAQ (4)
What does CKD Stage 3a mean?
Stage 3a indicates mildly to moderately decreased kidney function with a GFR between 45 and 59 mL/min/1.73m².
Why do adults and children use different formulas?
Children's muscle mass and body proportions change rapidly with height, making height-dependent formulas like Bedside Schwartz necessary.
What eGFR means kidney failure?
Below 15 mL/min/1.73m² (stage G5, kidney failure): urgent nephrology care, usually dialysis or transplant evaluation. Even 15–29 (G4, severe) already needs a specialist plan — never read one value alone, trends and albuminuria decide.
Can dehydration or creatine change my eGFR?
Yes, but temporarily: dehydration concentrates creatinine and lowers eGFR, while creatine supplements, very protein-heavy meals and hard training raise creatinine without real kidney damage. Muscular people also read higher. Retest well-hydrated and watch the trend, not one number.
Sources & References
⚠ Health Disclaimer
This tool provides estimates for informational purposes only and does not constitute medical, veterinary, or professional advice. Always consult a qualified healthcare professional before making decisions about your health or treatment.