GFR Calculator
Estimate glomerular filtration rate based on relevant health measurements.
Understanding GFR Calculator
The Glomerular Filtration Rate (GFR) is one of the most commonly used measures for evaluating how effectively the kidneys filter waste products and excess substances from the blood. Because directly measuring GFR is complex and usually requires specialized testing, healthcare professionals commonly use an estimated GFR, or eGFR, calculated from laboratory and demographic information. eGFR is reported in milliliters per minute per 1.73 square meters of body surface area (mL/min/1.73 m²).
This calculator estimates GFR using the 2021 CKD-EPI creatinine equation for adults. The equation uses age, sex, and standardized serum creatinine concentration and does not include race as a calculation factor. Serum creatinine is a waste product produced partly from normal muscle metabolism and removed from the bloodstream by the kidneys. When kidney filtration decreases, serum creatinine may increase, although creatinine levels can also be affected by muscle mass, diet, certain medications, hydration, and other individual factors.
A practical way to use this calculator
To use GFR Calculator effectively, enter the values requested by the calculator and keep their units and meaning consistent. The main information requested on this page includes Age (years), Gender, Serum Creatinine (mg/dL). If the calculator offers selectable methods or options, choose the one that matches the question you are trying to answer.
What can change the answer
The result is calculated from the inputs shown on this page, so it is most useful when you understand what each input represents. Before relying on the number, check the units, the scale of the result, and any assumptions described above the calculator.
About GFR Calculator
The Glomerular Filtration Rate (GFR) is one of the most commonly used measures for evaluating how effectively the kidneys filter waste products and excess substances from the blood. Because directly measuring GFR is complex and usually requires specialized testing, healthcare professionals commonly use an estimated GFR, or eGFR, calculated from laboratory and demographic information. eGFR is reported in milliliters per minute per 1.73 square meters of body surface area (mL/min/1.73 m²).
This calculator estimates GFR using the 2021 CKD-EPI creatinine equation for adults. The equation uses age, sex, and standardized serum creatinine concentration and does not include race as a calculation factor. Serum creatinine is a waste product produced partly from normal muscle metabolism and removed from the bloodstream by the kidneys. When kidney filtration decreases, serum creatinine may increase, although creatinine levels can also be affected by muscle mass, diet, certain medications, hydration, and other individual factors.
The calculated eGFR should be interpreted as an estimate rather than a direct measurement of kidney filtration. The same creatinine value can correspond to different estimated GFR values depending on age and sex. For this reason, an eGFR result should not be interpreted by looking at creatinine alone.
Understanding Your eGFR Result
eGFR results are commonly grouped into categories ranging from G1 to G5. These categories describe the estimated level of kidney filtration, but they do not provide a complete diagnosis by themselves. Kidney health is also evaluated using other information, particularly urine albumin and evidence of kidney damage.
≥90 mL/min/1.73 m²
G2 — Mildly Decreased
60–89 mL/min/1.73 m²
G3a — Mildly to Moderately Decreased
45–59 mL/min/1.73 m²
G3b — Moderately to Severely Decreased
30–44 mL/min/1.73 m²
G4 — Severely Decreased
15–29 mL/min/1.73 m²
G5 — Kidney Failure Range
<15 mL/min/1.73 m²
How the GFR Calculation Works
The calculator uses serum creatinine together with age and sex to estimate kidney filtration. The calculation uses different coefficients depending on sex and applies the relationship between creatinine concentration and estimated filtration rate.
In the equation, SCr represents standardized serum creatinine in mg/dL. The value of κ is 0.7 for females and 0.9 for males, while α is −0.241 for females and −0.302 for males. The equation is intended for adults and is based on the 2021 CKD-EPI creatinine equation.
Why Serum Creatinine Matters
Creatinine is produced continuously by the body and is normally removed from the blood by the kidneys. Because kidney filtration is one of the major factors affecting creatinine concentration, serum creatinine is useful for estimating GFR. However, creatinine is not a perfect marker of filtration. People with unusually high or low muscle mass, certain dietary patterns, or medications that affect creatinine handling may have creatinine values that do not correspond precisely to their actual filtration rate.
eGFR and Kidney Health
A lower eGFR can be associated with reduced kidney filtration, but a single result should not automatically be interpreted as chronic kidney disease. Kidney disease is assessed using the overall clinical picture, including whether abnormalities persist over time and whether other markers of kidney damage are present. For this reason, trends in eGFR can be more informative than relying on one isolated result.
Urine albumin, particularly the urine albumin-to-creatinine ratio, can provide important additional information about kidney health. Someone with an eGFR in the normal or mildly decreased range may still require further evaluation if other evidence of kidney damage is present.
Example Calculation
Gender: Male
Serum Creatinine: 1.00 mg/dL
Using the 2021 CKD-EPI creatinine equation:
Estimated eGFR ≈ 98 mL/min/1.73 m²
GFR Category: G1 — Normal or High
What Can Affect eGFR?
Estimated GFR can be influenced by factors beyond kidney filtration. Serum creatinine may vary with muscle mass, recent dietary intake, certain medications, and other biological factors. Laboratory measurement differences can also affect the calculated estimate. Consequently, eGFR should be interpreted in the context of the person's overall health and laboratory history.
When eGFR Is Most Useful
eGFR is commonly used to monitor kidney function over time, help identify possible reductions in kidney filtration, and provide information that can be considered alongside urine testing and other clinical findings. Repeated measurements can help show whether kidney function is relatively stable or changing over time.
This calculator is designed as an educational estimation tool for adults. It should not be used by itself to diagnose chronic kidney disease, determine treatment, or make medication decisions. Clinical interpretation should consider laboratory trends, urine findings, medical history, medications, and other relevant factors.
Medical Disclaimer
This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional for medical decisions.