GFR Calculator for Adults

Formula	Result
MDRD 4-Variable Equation	89.3 mL/min/1.73 m²
CKD-EPI Formula	99.2 mL/min/1.73 m²
Mayo Quadratic Formula	120.3 mL/min/1.73 m²

Stage	GFR Value (mL/min/1.73 m²)
Normal	90+ or above and no proteinuria
CKD1	90+ with evidence of kidney damage
CKD2 (Mild)	60 to 89 with evidence of kidney damage
CKD3 (Moderate)	30 to 59
CKD4 (Severe)	15 to 29
CKD5 Kidney failure	less than 15

Complete GFR Calculator Guide & Information

1. What is GFR?

Glomerular Filtration Rate (GFR) is a measure of how well the kidneys filter waste from the blood. It represents the volume of fluid filtered from the renal glomerular capillaries into the Bowman's capsule per unit of time. GFR is considered the best overall measure of kidney function and is used to diagnose and stage chronic kidney disease (CKD).

Because directly measuring GFR is complex and expensive, it is typically estimated using equations based on serum creatinine levels, age, gender and race. These estimated values are referred to as eGFR (estimated GFR).

2. Calculation Formulas

MDRD 4-Variable Equation

            eGFR = 175 × (SCr)−1.154 × (age)−0.203 × [0.742 if female] × [1.212 if Black]
            
            Units: mL/min/1.73 m² | SCr in mg/dL

Developed by the Modification of Diet in Renal Disease study group. Widely used for staging CKD but tends to underestimate GFR at higher levels of kidney function.

CKD-EPI Formula (2009)

            Male:

            If SCr ≤ 0.9: eGFR = 141 × (SCr/0.9)−0.411 × 0.993age × [1.159 if Black]

            If SCr > 0.9: eGFR = 141 × (SCr/0.9)−1.209 × 0.993age × [1.159 if Black]

            Female:

            If SCr ≤ 0.7: eGFR = 144 × (SCr/0.7)−0.329 × 0.993age × [1.159 if Black]

            If SCr > 0.7: eGFR = 144 × (SCr/0.7)−1.209 × 0.993age × [1.159 if Black]

Chronic Kidney Disease Epidemiology Collaboration formula. More accurate than MDRD at higher GFR levels and is now the recommended equation by most kidney disease organizations including KDIGO.

Mayo Quadratic Formula

            eGFR = exp( 1.911 + 5.249/SCr − 2.114/SCr² − 0.00686 × age − 0.205 × [if female] )
            
            Units: mL/min/1.73 m² | SCr in mg/dL

Developed at the Mayo Clinic. Uses a quadratic relationship between creatinine and GFR. Tends to produce higher estimates than MDRD, particularly at normal to near-normal kidney function.

3. Serum Creatinine Units

Unit	Conversion	Typical Normal Range
mg/dL	1 mg/dL = 88.4 μmol/L	0.6 – 1.2 mg/dL (adults)
μmol/L	1 μmol/L = 0.0113 mg/dL	53 – 106 μmol/L (adults)

4. CKD Stage Classification

Stage	GFR Range	Description	Clinical Action
Normal	≥ 90	Normal kidney function	Routine monitoring
CKD 1	≥ 90 with damage	Kidney damage with normal function	Diagnose and treat cause
CKD 2 (Mild)	60 – 89	Mildly decreased function	Estimate progression rate
CKD 3 (Moderate)	30 – 59	Moderately decreased function	Evaluate and treat complications
CKD 4 (Severe)	15 – 29	Severely decreased function	Prepare for renal replacement therapy
CKD 5 (Failure)	< 15	Kidney failure / end-stage renal disease	Dialysis or transplantation

5. Important Limitations

GFR estimates are less accurate in extremes of age, body size, muscle mass and pregnancy.
Creatinine-based equations can be inaccurate in people with very high or very low muscle mass, amputees, or people on vegetarian diets.
Race adjustment is a subject of ongoing clinical debate. This calculator includes the traditional race coefficients for completeness.
Acute changes in serum creatinine (acute kidney injury) invalidate steady-state eGFR calculations.
All three equations are calibrated to specific creatinine assays. Results may vary between laboratories.

6. Input & Control Definitions

Serum creatinine (S_Cr): Blood creatinine level. Select unit: mg/dL or μmol/L.
Age: Patient age in years. For adult use only (18+).
Gender: Male or female — creatinine production differs by gender.
Race: Black or Not Black — race coefficients used in MDRD and CKD-EPI equations.
Calculate Button: Computes all three GFR formulas and updates the stage indicator.
Clear Button: Resets all inputs to default values.

7. Medical Disclaimer

This calculator is for educational and informational purposes only. It is NOT a substitute for professional medical advice, diagnosis or treatment. GFR estimates are approximations and should always be interpreted by a qualified healthcare provider in the context of the full clinical picture.

Do not make medical decisions based solely on these calculations. Always consult a nephrologist or qualified healthcare professional for kidney function assessment and management.

8. References

1. Levey AS, et al. "A more accurate method to estimate glomerular filtration rate from serum creatinine: a new prediction equation." Modification of Diet in Renal Disease Study Group. Ann Intern Med. 1999.
2. Levey AS, et al. "A new equation to estimate glomerular filtration rate." CKD-EPI Investigators. Ann Intern Med. 2009.
3. Rule AD, et al. "Using serum creatinine to estimate glomerular filtration rate: accuracy in good health and in chronic kidney disease." Mayo Clin Proc. 2004.
4. KDIGO Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. 2012.
5. National Kidney Foundation. KDOQI Clinical Practice Guidelines and Clinical Practice Recommendations for Diabetes and Chronic Kidney Disease. 2012.