Glomerular Filtration Rate (eGFR) Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/5/2026
Estimated glomerular filtration rate (eGFR) measures how efficiently your kidneys filter your blood. It's calculated from serum creatinine, age, and sex using the CKD-EPI 2021 equation; a value of 90 mL/min/1.73m² or above corresponds to normal or high kidney function.
Explanation
Glomerular filtration rate (GFR) measures the volume of blood the kidneys filter each minute to remove waste from the body — a key indicator of kidney function. Measuring it directly is complex and invasive; in practice, it is ESTIMATED (hence eGFR) from serum creatinine, a muscle waste product whose blood concentration indirectly reflects how efficiently the kidneys are filtering, combined with age and sex to account for natural variation in muscle mass. This calculator uses the CKD-EPI 2021 equation, the current reference recommended by US nephrology professional societies since it replaced the 2009 version, which included a race coefficient now abandoned for lack of solid scientific justification. One essential point to understand before interpreting a result: a lowered eGFR from a single measurement is never enough on its own to diagnose chronic kidney disease, which by definition requires a confirmed abnormality over at least 3 months, not a single isolated value — many temporary factors (dehydration, certain recent medications, intense muscular exertion the day before) can transiently lower creatinine or eGFR without reflecting a lasting kidney problem. This calculator gives a classification benchmark (the G1 to G5 stages of the international KDIGO classification), never a diagnosis: only a healthcare professional, considering the complete history and further testing if needed, can interpret this result in its real medical context. For another routine health indicator, see our body fat percentage calculator.
Example: a 50-year-old man with creatinine at 88.4 µmol/L
Inputs
Creatinine: 88.4 µmol/L (1.0 mg/dL). Age: 50. Sex: male.
Calculation
Converted creatinine: 88.4 ÷ 88.4 = 1.0 mg/dL. Creatinine/κ ratio: 1.0 ÷ 0.9 ≈ 1.111 (above 1, so the formula's "max" branch applies with the −1.2 exponent): 1.111^(−1.2) ≈ 0.8812. Age factor: 0.9938^50 ≈ 0.7327. eGFR = 142 × 0.8812 × 0.7327 × 1 (no female factor) ≈ 91.7.
Result
The estimated GFR for this profile is about 91.7 mL/min/1.73m², a normal or high kidney function level (G1).
Frequently asked questions
Does a lowered eGFR always mean kidney disease?
No, not from a single measurement. A chronic kidney disease diagnosis requires a confirmed abnormality over at least 3 months, and generally other findings (proteinuria, imaging) as well. Many temporary factors (dehydration, certain medications, recent intense muscular exertion) can transiently lower eGFR without reflecting a lasting kidney problem: only a healthcare professional can confirm or rule out a diagnosis from the complete history.
Why doesn't the 2021 version of this formula use a race coefficient anymore?
Because the older coefficient, introduced in the 2009 version based on average differences observed between population groups, turned out to rest on insufficient scientific justification and could delay access to nephrology care for some patients by overestimating their real kidney function. The 2021, race-free version is now the reference recommended by US nephrology professional societies.
Why isn't creatinine alone enough to assess kidney function?
Because creatinine also depends on muscle mass: for the same kidney function, a very muscular person produces more creatinine than someone with low muscle mass, which would distort a raw creatinine reading on its own. The CKD-EPI equation partly corrects for this bias by factoring in age and sex, variables correlated with average muscle mass, but remains less precise than a direct measurement for atypical cases (a very unusual muscle mass, for example).
Is there a link between kidney function and blood pressure?
Yes, a close, two-way link: poorly controlled high blood pressure over time can damage the kidneys, and conversely, impaired kidney function can itself contribute to raising blood pressure. See our blood pressure calculator to see where your reading falls relative to reference categories.