eGFR and CKD Risk Calculator (KDIGO Grid)

What Is eGFR?

The estimated Glomerular Filtration Rate (eGFR) measures how well your kidneys filter waste from the blood.
The glomeruli are tiny filtering units inside the kidneys, and a healthy adult has about a million per kidney. eGFR is reported in mL/min/1.73m², the volume of blood filtered per minute, normalised to a standard body surface area.
A healthy young adult typically has an eGFR of 90–120 mL/min/1.73m².

What this page adds

The eGFR on its own is half of a kidney check. KDIGO (Kidney Disease: Improving Global Outcomes) stages chronic kidney disease on two axes: the eGFR, and the amount of albumin leaking into the urine, measured as the urine albumin-to-creatinine ratio (ACR). This calculator takes both and places you on KDIGO’s risk grid. Leave the ACR blank and you get the eGFR alone, the same figure as the GFR calculator, which also shows the older MDRD equation and how far creatinine has to move to change your stage.

The CKD-EPI Equation (2021)

The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) published an updated race-free equation in 2021.
The National Kidney Foundation and the American Society of Nephrology recommended it for every US lab that year. The UK’s NICE still uses the 2009 CKD-EPI equation with its race term removed, and some European labs use the newer EKFC equation, so a result from abroad can differ by a few points.
eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^Age
For females, multiply by 1.012.
Where: Scr = serum creatinine (mg/dL; divide µmol/L by 88.4), κ = 0.7 (females) or 0.9 (males), α = −0.241 (females) or −0.302 (males).

CKD Stages by eGFR

Normal or high (Stage G1): eGFR ≥ 90. Kidney damage may still be present, but filtration is normal.
Mildly decreased (Stage G2): eGFR 60 to 89. Mild reduction, monitored annually.
Mildly to moderately decreased (Stage G3a): eGFR 45 to 59. Nephrology referral if other risk factors are present.
Moderately to severely decreased (Stage G3b): eGFR 30 to 44. Nephrology referral recommended.
Severely decreased (Stage G4): eGFR 15 to 29. Preparation for kidney replacement therapy begins here.
Kidney failure (Stage G5): eGFR below 15. Dialysis or transplant may be required.

Albuminuria stages and the risk grid

A1, normal to mildly increased: ACR under 30 mg/g (under 3 mg/mmol).
A2, moderately increased: 30 to 300 mg/g (3 to 30 mg/mmol).
A3, severely increased: over 300 mg/g (over 30 mg/mmol).

The risk is of kidney failure, heart disease and death together, which is why albumin matters so much: someone with an eGFR of 75 and an ACR of 400 sits in a higher-risk box than someone with an eGFR of 50 and normal urine. The grid also explains a common surprise. An eGFR of 70 with an ACR under 30 is not chronic kidney disease at all; it takes albuminuria, another marker of kidney damage, or an eGFR under 60 lasting three months.

What Is Creatinine?

Creatinine is a waste product produced by muscle metabolism at a constant rate.
Healthy kidneys filter it efficiently, so a high blood creatinine means the kidneys are not clearing it.
Normal serum creatinine: 0.7–1.2 mg/dL (males), 0.5–1.0 mg/dL (females).
Creatinine can be temporarily elevated by intense exercise, high meat intake, or dehydration.
Cystatin C is an alternative marker, less affected by muscle mass, and is sometimes run alongside creatinine.

Factors That Affect eGFR

Age: eGFR naturally declines by about 1 mL/min/year after age 40.
Muscle mass: very muscular individuals produce more creatinine and may have lower calculated eGFR.
Pregnancy: true GFR rises by up to about half during pregnancy, and the equation is not valid then, so it misreads pregnant women.
Medications: NSAIDs, ACE inhibitors, and certain antibiotics can temporarily reduce eGFR.

When to See a Doctor

Single eGFR values should always be confirmed with repeat testing. eGFR below 60, or an ACR of 30 mg/g or more, on two measurements ≥ 3 months apart confirms chronic kidney disease.
KDIGO advises referral to a kidney specialist for an eGFR below 30 or an ACR persistently over 300 mg/g (30 mg/mmol). Below 15 may require transplant evaluation.

Disclaimer

This calculator is for educational purposes only. Consult a licensed physician for medical evaluation.