ZOVATOOL

GFR Calculator

GFR (CKD-EPI 2021)
97.6 mL/min/1.73m²
G1 — Normal
MDRD
82.8
mL/min/1.73m²
Cockcroft-Gault
104.2
mL/min
Reference: KDIGO CKD stages
G1 ≥90 normal · G2 60–89 mild · G3a 45–59 · G3b 30–44 · G4 15–29 · G5 <15
⚠ Educational use only — clinical decisions require a doctor.

How to use the GFR Calculator

  1. Enter serum creatinine (mg/dL or µmol/L — calculator auto-detects).
  2. Enter age, sex.
  3. Select formula: CKD-EPI 2021 (current gold standard, race-free), MDRD, or Cockcroft-Gault (for drug dosing).
  4. For Cockcroft-Gault: also enter weight.
  5. Read eGFR in mL/min/1.73 m² and CKD stage (G1–G5).
  6. Cross-check across formulas — CKD-EPI is preferred for staging; Cockcroft-Gault for drug dosing.
  7. Review CKD stage classification and clinical implications.
  8. See suggested nephrology referral thresholds (eGFR < 30 = mandatory referral).
  9. Track eGFR over time to spot decline (>3 mL/min/year is worrying).
  10. Export to add to patient chart or personal medical record.
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GFR: the number that defines your kidney health

Glomerular Filtration Rate (GFR) is the volume of blood filtered by the kidneys per minute, normalized to a standard body surface area of 1.73 m². It's the single best measure of overall kidney function and the metric that defines Chronic Kidney Disease (CKD) staging worldwide. Normal is ≥90 mL/min/1.73 m². Below 60 for 3+ months defines CKD. Below 15 is kidney failure requiring dialysis or transplant.

Measuring true GFR is expensive and time-consuming (inulin clearance). Estimated GFR (eGFR) from serum creatinine is the routine clinical alternative. The CKD-EPI 2021 equation is now the international gold standard — it removed the race coefficient present in earlier formulas, which had inappropriately over-estimated GFR in Black patients and delayed nephrology referral, transplant listing and drug dose adjustments. Every major US institution adopted the race-free version by 2023.

CKD staging drives clinical action. G1 (≥90) and G2 (60–89) with kidney damage markers (protein in urine, structural abnormalities) are the earliest CKD stages — often invisible to the patient but requiring blood pressure and glucose control. G3a (45–59) and G3b (30–44) need medication dose adjustments and specialist follow-up. G4 (15–29) triggers transplant workup. G5 (<15) is end-stage renal disease.

Creatinine clearance (Cockcroft-Gault, 1976) predates eGFR and is still used for drug dosing — especially aminoglycosides, DOACs (apixaban, rivaroxaban), and some chemotherapy. It uses serum creatinine, age, weight and sex. Doses of dabigatran, for example, are reduced or contraindicated below certain CrCl thresholds. Prescribers should use CrCl (not eGFR) for these medications, per FDA labeling.

GFR isn't fixed — it declines about 1 mL/min per year after age 40 in most adults. Faster decline (>3 mL/min/year) warrants investigation. Slowing progression: control blood pressure to <130/80 (ACE inhibitors and ARBs are first-line), control glucose in diabetics (SGLT2 inhibitors slow CKD dramatically per DAPA-CKD and EMPA-KIDNEY trials), stop smoking, avoid NSAIDs when GFR is impaired, and treat sleep apnea. Regular monitoring — annual eGFR plus urine albumin/creatinine ratio — catches decline early enough to preserve kidney function for decades.