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GFR Calculator,
kidney function estimate.

Estimate your glomerular filtration rate (eGFR) from serum creatinine, age, and sex using the CKD-EPI 2021 equation — the current clinical standard. Results include your CKD stage, kidney function percentage, and an MDRD comparison, with a colour-coded stage spectrum and full reference table.

How it worksCKD-EPI 2021

Inputs

Lab values

Creatinine unit

Sex assigned at birth

Used in the CKD-EPI equation. Select whichever matches the lab order.

Serum creatinine (mg/dL)

mg/dL

Age

CKD-EPI 2021 eGFR: 94.6 mL/min/1.73m²
MDRD eGFR: 80.8 mL/min/1.73m²
CKD stage: G1

eGFR · CKD-EPI 2021

mL/min/1.73m²

94.6

G1 · Normal or highNormal or high kidney function

Kidney function

≥ 90%

of normal (est.)

GFR spectrum

0 – 130+

FailureSevereModerateNormal

CKD Stage

Normal or high kidney function

MDRD eGFR

80.8

mL/min/1.73m² (race-free MDRD)

Kidney function

≥ 90%

of normal — estimated from stage

Reference

CKD stages by eGFR (KDIGO 2024)

Stage	eGFR range	Description	Function
G1You	≥ 90	Normal or high kidney function	≥ 90%
G2	60–89	Mildly decreased kidney function	60–89%
G3a	45–59	Mildly to moderately decreased	45–59%
G3b	30–44	Moderately to severely decreased	30–44%
G4	15–29	Severely decreased kidney function	15–29%
G5	0–14	Kidney failure (or dialysis/transplant)	< 15%

Medical disclaimer — This calculator estimates eGFR using the CKD-EPI 2021 equation and is intended for educational purposes only. A single eGFR measurement is not sufficient to diagnose CKD. Your physician will evaluate results in the context of two or more measurements at least 3 months apart, along with urine albumin, imaging, and clinical history. Never use this tool as a substitute for professional medical advice.

Kidney function guide

What your eGFR means and how to read the results.

The glomerular filtration rate (GFR) measures how efficiently your kidneys filter waste products from the blood each minute. Because directly measuring GFR requires intravenous clearance markers, clinicians use the estimated GFR (eGFR): a calculated value derived from a simple blood test (serum creatinine) combined with demographic factors. A normal eGFR is approximately 90–120 mL/min/1.73 m² for a healthy young adult; eGFR naturally declines by roughly 1 mL/min/1.73 m² per year after age 40.

The CKD-EPI 2021 equation: the current gold standard

This calculator uses the CKD-EPI 2021 (Chronic Kidney Disease Epidemiology Collaboration) equation, published in the New England Journal of Medicine and adopted by the American Society of Nephrology, the National Kidney Foundation, and KDIGO guidelines. The 2021 update removed the race coefficient that was present in the 2009 equation, improving equity across diverse populations.

eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^(−1.200) × 0.9938^Age × [1.012 if female]

Where Scr is serum creatinine in mg/dL, κ = 0.7 (female) or 0.9 (male), and α = −0.241 (female) or −0.302 (male). The constant 0.9938^Age captures the gradual physiological decline in GFR with age.

The result is reported in mL/min/1.73 m² — normalised to a standard body surface area so that results are comparable across people of different body sizes.

What is serum creatinine?

Creatinine is a waste product produced at a constant rate by muscle metabolism. Healthy kidneys clear it from the blood at a steady rate; when kidney function declines, creatinine accumulates and blood levels rise.

Normal serum creatinine ranges (approximate):

Group	mg/dL	μmol/L
Adult male	0.74–1.35	65–120
Adult female	0.59–1.04	52–92
Elderly (> 70 yr)	0.60–1.30	53–115
Athlete / high muscle	May be higher	due to muscle mass

Creatinine alone is not a reliable kidney marker — a very muscular person may have a high creatinine with normal kidneys, while a frail elderly person may have normal creatinine with significantly reduced function. The CKD-EPI equation accounts for these differences through its age and sex coefficients.

CKD stages: what each level means

The Kidney Disease: Improving Global Outcomes (KDIGO) 2024 guidelines classify chronic kidney disease into six stages based on eGFR. Note that CKD is diagnosed when kidney abnormalities persist for ≥ 3 months: a single eGFR measurement below 60 does not automatically confirm CKD.

Stage	eGFR (mL/min/1.73m²)	Description	Typical management
G1	≥ 90	Normal or high	Monitor risk factors (diabetes, hypertension)
G2	60–89	Mildly decreased	Risk factor reduction; repeat testing in 12 mo
G3a	45–59	Mild–moderate decrease	Nephrology referral recommended; manage complications
G3b	30–44	Moderate–severe decrease	Nephrology care; prepare for progressive disease
G4	15–29	Severely decreased	Kidney replacement therapy (KRT) planning
G5	< 15	Kidney failure	Dialysis or transplant evaluation underway

Normal eGFR decline with age

GFR decreases naturally as part of ageing, even in healthy adults with no kidney disease. The typical decline is approximately 0.75–1 mL/min/1.73 m² per year after age 40. This means a 70-year-old with an eGFR of 65 may simply have age-appropriate kidney function, not CKD.

Age group	Average healthy eGFR	Note
20–29	~116	Peak function
30–39	~107	Modest decline begins
40–49	~99	Decline accelerates slightly
50–59	~93	Still well within normal
60–69	~85	Low end of G1 common
70–79	~75	G2 common without disease
≥ 80	~60–70	eGFR < 60 may be age-related

CKD-EPI 2021 vs. MDRD — what's the difference?

This calculator shows both equations. Here is how they compare:

CKD-EPI 2021 is more accurate at higher eGFR values (≥ 60 mL/min/1.73 m²), where MDRD tends to underestimate kidney function. It is the preferred equation by KDIGO, ASN, and NKF, and is used by most clinical labs in the United States and Europe. It is race-free (the 2021 update removed the race coefficient from the 2009 equation).
MDRD (4-variable) was developed in 1999 and performed well in populations with known CKD (eGFR < 60). It tends to underestimate GFR in people with normal or mildly reduced function. This calculator uses the race-free MDRD variant (without the Black race coefficient).

For most clinical purposes, the CKD-EPI 2021 result is the relevant one. The MDRD value is shown for comparison only.

Common causes of reduced kidney function

A persistently low eGFR (below 60) warrants investigation for underlying causes. The most common are:

Diabetic nephropathy: the leading cause of CKD globally; elevated blood glucose damages the kidney's filtering units over years.
Hypertensive nephrosclerosis: chronic high blood pressure stiffens and narrows blood vessels in the kidney, reducing filtration capacity.
Glomerulonephritis: inflammation of the glomeruli from immune-mediated diseases (IgA nephropathy, lupus nephritis, FSGS, etc.).
Polycystic kidney disease (PKD): inherited disorder where fluid-filled cysts replace kidney tissue.
Obstruction: kidney stones, enlarged prostate, or tumours blocking urine flow can impair filtration.
Nephrotoxic medications: NSAIDs, aminoglycoside antibiotics, contrast dye, and certain chemotherapy agents.

How to protect and improve kidney function

For most people with mildly reduced eGFR, lifestyle measures can slow or halt progression:

Control blood pressure. Target below 130/80 mmHg (or 120/80 in higher-risk patients per AHA guidelines). ACE inhibitors or ARBs have specific kidney-protective effects.
Optimise blood sugar. For diabetic patients, an HbA1c target of ≤ 7% substantially reduces nephropathy progression.
Reduce dietary sodium and protein. A low-sodium diet (≤ 2 g/day) reduces blood pressure and proteinuria. Modest protein restriction (0.8 g/kg/day) can slow CKD progression in stages 3–5.
Avoid nephrotoxins. Limit NSAID use, ensure adequate hydration with contrast procedures, and discuss all medications with your nephrologist.
Stay hydrated. Adequate fluid intake supports normal tubular function and reduces stone risk.
Quit smoking and limit alcohol. Smoking independently accelerates CKD progression; heavy alcohol use raises blood pressure and IgA nephropathy risk.

FAQ

Frequently asked

What is a normal GFR?+

For adults under 40, a normal eGFR is typically 90–120 mL/min/1.73 m². GFR naturally declines with age — an eGFR of 65–75 in a 70-year-old may simply reflect age-related decline rather than kidney disease. CKD is not diagnosed solely on eGFR; it requires evidence of kidney damage persisting for at least 3 months.

What does a low eGFR mean?+

An eGFR consistently below 60 mL/min/1.73 m² for at least 3 months meets the definition of Chronic Kidney Disease (CKD). The lower the eGFR, the more advanced the disease. A single low reading may reflect acute illness, dehydration, or medication effects — repeat testing is required before a diagnosis is made.

Why does sex affect the eGFR calculation?+

Men typically have more muscle mass than women and therefore produce more creatinine per kilogram of body weight. The CKD-EPI equation uses different κ (kappa) and α (alpha) coefficients for males and females to account for this baseline difference, as well as a 1.2% female multiplier.

What is the difference between CKD-EPI 2021 and MDRD?+

CKD-EPI 2021 is the current gold standard, more accurate at GFR ≥ 60, and race-free. The MDRD equation from 1999 was widely used for decades but systematically underestimates GFR in healthy people. Both are shown here for comparison; clinical decisions should be based on CKD-EPI 2021.

Can GFR improve?+

Yes, in some situations. Treating the underlying cause (e.g., controlling blood pressure or blood sugar), stopping nephrotoxic drugs, or resolving dehydration can restore eGFR. In chronic kidney disease, slowing progression is the primary goal; significant reversal is less common but possible in early stages with aggressive management.

Do I need a referral to a nephrologist?+

KDIGO guidelines suggest referral for eGFR persistently below 45 (Stage G3b), any eGFR below 30, rapid decline (> 5 mL/min/1.73 m² per year), significant proteinuria (urine albumin:creatinine ≥ 300 mg/g), difficult-to-control hypertension, or evidence of hereditary kidney disease.

Is eGFR different from 24-hour urine creatinine clearance?+

Yes. Measured creatinine clearance from a 24-hour urine collection is more precise but cumbersome. eGFR from the CKD-EPI equation correlates well with measured GFR and is sufficient for clinical staging. Measured clearance is sometimes used to confirm eGFR before medication dosing adjustments or transplant evaluation.

Should I fast before a creatinine blood test?+

Fasting is not required for a creatinine measurement. However, eating a large meal high in cooked meat (which converts creatine to creatinine during cooking) can transiently raise serum creatinine by up to 0.1–0.2 mg/dL. For the most consistent results, the test is usually drawn in the morning before heavy physical activity.

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