GFR / eGFR Calculator

Understanding eGFR and CKD Staging

Glomerular Filtration Rate (GFR) measures how much blood the kidneys filter per minute — it is the best overall indicator of kidney function. Because direct GFR measurement requires complex testing, estimated GFR (eGFR) is calculated from serum creatinine, age, and sex using validated equations.

CKD-EPI 2021 Equation (Recommended)

The CKD-EPI 2021 equation is the current recommended standard from KDIGO and NIDDK. The 2021 version removed the race coefficient from earlier CKD-EPI equations, improving equity across populations. It is more accurate than MDRD for eGFR values above 60 mL/min/1.73m².

MDRD Equation (4-Variable)

The Modification of Diet in Renal Disease (MDRD) equation is an older but widely used formula. It tends to underestimate GFR in patients with normal or near-normal kidney function. It is still used in some laboratory reporting systems but is being phased out in favour of CKD-EPI 2021.

KDIGO CKD Staging

• G1 — Normal: eGFR ≥90 mL/min/1.73m² — Normal or high kidney function
• G2 — Mildly Decreased: eGFR 60–89 — Monitor, manage risk factors
• G3a — Mildly-Moderately Decreased: eGFR 45–59 — Nephrology referral consider
• G3b — Moderately-Severely Decreased: eGFR 30–44 — Nephrology referral recommended
• G4 — Severely Decreased: eGFR 15–29 — Prepare for renal replacement therapy
• G5 — Kidney Failure: eGFR <15 — Dialysis or transplant required

For patients with reduced eGFR, use our drug dosage calculator to adjust renally-cleared medications. Monitor blood pressure closely using our blood pressure tracker — hypertension is both a cause and consequence of CKD. For IV fluid management, use our IV drip rate calculator and fluid balance calculator.

⚠️ eGFR is an estimate and should be interpreted alongside clinical context. A single value does not diagnose CKD — the diagnosis requires evidence of kidney damage or reduced eGFR persisting for more than 3 months. Always consult a nephrologist for clinical decisions.