GFR Calculator
Estimate glomerular filtration rate and CKD stage using CKD-EPI and MDRD.
About GFR Calculator
The GFR (glomerular filtration rate) measures how well the kidneys filter waste from the blood. eGFR is estimated from serum creatinine, age and sex. The CKD-EPI 2021 equation is the current clinical standard; it is race-free (the earlier 2009 version had a race coefficient that has been removed). MDRD is an older formula included for reference; it underestimates GFR in people with mild kidney impairment.
Formulas
CKD-EPI 2021
eGFR = 142 × min(Scr/κ,1)^α × max(Scr/κ,1)^(−1.2) × 0.9938^Age × Sf
- Scr
- Serum creatinine (mg/dL)
- κ
- 0.7 (female), 0.9 (male)
- α
- −0.241 (female), −0.302 (male)
- Sf
- 1.012 (female), 1.0 (male)
MDRD 4-variable
eGFR = 175 × Scr^(−1.154) × Age^(−0.203) × [0.742 if female]
Worked example
With the default values below, GFR Calculator returns eGFR (CKD-EPI 2021) of 89.8. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Serum creatinineaccepts 10–2,000
- 90
- Creatinine unitone of µmol/L, mg/dL
- µmol/L
- Age (years)accepts 18–120
- 50
- Biological sex at birthone of Male, Female
- Male
Results
- eGFR (CKD-EPI 2021)
- 89.8 mL/min/1.73 m²
- eGFR (MDRD)Tends to underestimate GFR in people with normal or near-normal kidney function.
- 77.5 mL/min/1.73 m²
- CKD stage (per CKD-EPI)
- G2
- Stage description
- Mildly decreased (60–89)
- Creatinine (mg/dL)
- 1.02
- Creatinine (µmol/L)
- 90.0
Step by step
- 1Serum creatinine= 1.02 mg/dL (90.0 µmol/L)
- 2CKD-EPI 2021 (race-free)= 89.8 mL/min/1.73 m²
- 3MDRD (4-variable)= 77.5 mL/min/1.73 m²
- 4CKD stage (CKD-EPI)= G2 — Mildly decreased (60–89)
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
- This calculator estimates kidney function for informational and educational purposes. eGFR estimates from creatinine alone have limitations and should always be interpreted in the clinical context by a qualified healthcare provider. Do not make treatment decisions based solely on this estimate.
- This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
This calculator estimates kidney function for informational and educational purposes. eGFR estimates from creatinine alone have limitations and should always be interpreted in the clinical context by a qualified healthcare provider. Do not make treatment decisions based solely on this estimate.
Frequently Asked Questions
What is a normal GFR?
A GFR ≥ 60 mL/min/1.73 m² is generally considered normal for adults (CKD stages G1–G2). Note that GFR naturally declines with age — approximately 1 mL/min/1.73 m² per year after age 30.
Why is the CKD-EPI 2021 equation race-free?
The 2009 CKD-EPI equation included a racial coefficient that produced higher eGFR estimates for Black patients, delaying referrals to nephrology. The 2021 race-free version was developed to remove this bias and is now the recommended standard in the US, UK and elsewhere.
Why do CKD-EPI and MDRD give different results?
MDRD was developed in a population with moderate to severe kidney disease and systematically underestimates GFR above 60. CKD-EPI was developed from a broader population and performs better across the full range. When both are above 60, MDRD is less reliable.
Can I use this for children?
No. CKD-EPI and MDRD are validated for adults ≥ 18 years. Paediatric kidney function is estimated with the Schwartz equation, which uses height instead of age.