Estimate your glomerular filtration rate using the 2021 CKD-EPI race-free equation — see your eGFR, CKD stage (G1–G5), and understand what your kidney function result means.
This calculator is for people aged 18 years or older.
Glomerular filtration rate (GFR) measures how much fluid your kidneys filter per minute — it's the single most important number on a kidney function panel. Think of it as the rate at which your kidneys clear waste from your bloodstream. A higher GFR means your kidneys are filtering efficiently; a significant drop means less fluid is being cleaned per minute, signaling reduced kidney function.
In healthy adults under 40, the normal GFR range adjusted for body surface area is approximately 100–130 mL/min/1.73m² for men and 90–120 mL/min/1.73m² for women. After 40, GFR gradually declines with age — a normal physiological shift, not necessarily a disease — which is why age is built directly into the CKD-EPI equation this calculator uses.
The GFR Calculator is designed for adults who have a recent serum creatinine lab result and want to understand what their kidney function estimate means. You enter your serum creatinine (in mg/dL), your age (in years), and your biological sex. The tool applies the 2021 CKD-EPI creatinine equation to return your eGFR in mL/min/1.73 m², which is then mapped to a NKF CKD staging framework (G1–G5). The output also includes a plain-language interpretation of what your stage means for kidney health monitoring. This calculator does not include urine albumin data (the albuminuria component of full CKD staging) — for complete CKD staging, both eGFR and albuminuria need to be assessed clinically. Use this tool as a starting point for understanding your creatinine lab report, not as a replacement for a nephrology consultation.
Enter your serum creatinine value in mg/dL (found on any standard metabolic panel), your age, and your biological sex, then tap calculate. The result displays your eGFR in mL/min/1.73 m² and your corresponding CKD stage: G1 is ≥90 (normal/high), G2 is 60–89 (mildly decreased), G3a is 45–59, G3b is 30–44, G4 is 15–29, and G5 is <15 (kidney failure requiring dialysis or transplant evaluation). A higher number is always better. An eGFR of 60 or above with no markers of kidney damage generally does not indicate CKD on its own; the diagnosis requires either eGFR below 60 or evidence of kidney damage (elevated urine albumin, abnormal imaging, etc.) present for three or more months, per NKF/KDIGO guidelines.
The 2021 CKD-EPI creatinine equation (race-free) is the NKF-endorsed standard:
eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^(−1.200) × 0.9938^Age × (1.012 if female)
Scr = serum creatinine (mg/dL)
κ = 0.7 for females, 0.9 for males
α = −0.241 for females, −0.302 for males
min/max = minimum or maximum of Scr/κ or 1
In plain language: the formula adjusts creatinine for the natural difference in muscle mass between males and females (creatinine is produced by muscle, so sex affects baseline levels), then scales by age. A lower creatinine and a younger age both produce a higher eGFR.
This is one of the most-searched GFR questions, and the answer requires age context. eGFR naturally declines with age because kidney mass and nephron count decrease over a lifetime — this is a normal physiological change, not necessarily a disease process. A healthy 25-year-old might have an eGFR above 110; a healthy 70-year-old might have an eGFR of 65–75. The NKF notes that an eGFR in the G2 range (60–89) in an older adult without other markers of kidney disease may simply reflect age-related decline rather than true CKD. This is why age is built into the CKD-EPI equation and why eGFR alone, without clinical context, shouldn't trigger alarm. That said, an eGFR below 60 at any age warrants investigation, and a decline of more than 5 mL/min/1.73 m² per year is considered rapid and should be evaluated by a nephrologist.
The six CKD stages defined by the NKF and KDIGO map eGFR to progressively greater kidney function loss:
Normal or high kidney function. CKD at this stage requires another marker of damage (elevated urine albumin, structural abnormality) — an eGFR of 90 alone is healthy.
Mildly decreased. Often age-related. Monitoring is appropriate; no immediate intervention typically needed unless other damage markers are present.
Mild to moderately decreased. Annual monitoring, blood pressure management, and lifestyle modifications are standard care. Anemia and mineral metabolism changes begin to emerge.
Moderately to severely decreased. Nephrology referral is often recommended. Dietary phosphorus and protein management become important.
Severely decreased. Preparation for kidney replacement therapy (dialysis or transplant evaluation) begins. Anemia, bone disease, and cardiovascular risk are significant concerns.
Kidney failure. Dialysis or kidney transplant is required for survival. This stage may be called End-Stage Renal Disease (ESRD) or End-Stage Kidney Disease (ESKD).
Not all eGFR decline is irreversible. In the early stages — G1 through G3 — several well-documented interventions can slow progression or modestly improve kidney function. Blood pressure control is the most impactful single factor: the NKF recommends keeping blood pressure below 130/80 mmHg for adults with CKD, and ACE inhibitors or ARBs are often preferred because they reduce pressure inside the kidney's filtering units. Blood sugar management in people with diabetes dramatically slows diabetic nephropathy, the leading cause of CKD in the US. Dietary sodium reduction (targeting under 2,300 mg/day), moderation of dietary protein (excessive protein load increases filtration demand), and avoiding NSAIDs like ibuprofen (which reduce blood flow to the kidneys with regular use) are all evidence-supported steps. SGLT2 inhibitors — originally developed as diabetes drugs — have demonstrated significant kidney-protective effects and are now part of CKD management guidelines even in non-diabetic patients. Smoking cessation also has a meaningful impact on slowing CKD progression.
Before 2021, the widely used CKD-EPI equation included a race coefficient that estimated higher eGFR values for Black patients than for other racial groups based on assumed differences in muscle mass and creatinine production. The NKF and American Society of Nephrology jointly recommended removing the race adjustment in 2021 after research showed that the race-adjusted formula had led to delayed CKD diagnoses, delayed referrals to nephrology, and reduced access to transplant listings for Black patients. The new 2021 CKD-EPI creatinine equation produces the same eGFR for the same creatinine, age, and sex regardless of race — a clinically and ethically important change. This calculator uses the 2021 race-free equation. If you have a lab report that used the older race-adjusted formula, your eGFR result may differ slightly from what this calculator returns.
Serum creatinine is the primary input, and it's directly tied to muscle mass — people with greater muscle mass (typically men, athletes, and younger individuals) have higher baseline creatinine, which is why the formula adjusts for sex and age. Creatinine can spike transiently from intense exercise, dehydration, or a high-protein meal the day before the blood draw, producing a temporarily lower eGFR that doesn't reflect true kidney function. For the most accurate baseline reading, the test is typically ordered after overnight fasting and without recent intense exercise. Age progressively lowers eGFR even with healthy kidneys. Conditions that affect creatinine generation or muscle mass — muscular dystrophy, amputation, severe malnutrition — reduce creatinine and inflate eGFR, potentially masking true kidney impairment. In these cases, cystatin C-based eGFR equations are more reliable.
Thomas gets a routine metabolic panel. His creatinine is 1.3 mg/dL. Age 55, male. The calculator returns an eGFR of approximately 60 — Stage G2. His provider explains that at 55, a G2 reading warrants monitoring but is not necessarily CKD on its own without additional damage markers like elevated albumin in urine. They order a urine albumin-to-creatinine ratio (ACR) and schedule a follow-up in six months.
Sandra has a history of type 2 diabetes and gets a creatinine of 1.8 mg/dL. Age 67, female. The calculator returns an eGFR of approximately 33 — Stage G3b. This puts her in the moderately to severely decreased range, and her provider refers her to a nephrologist for evaluation, dietary guidance on phosphorus and protein, and an assessment of whether an SGLT2 inhibitor is appropriate for her kidney protection.
Use your most recent serum creatinine from a standard metabolic panel — ensure the test was done while you were well-hydrated and hadn't done intense exercise in the 24 hours before.
Enter your biological sex (not gender identity) for the calculation, since the equation's sex coefficient reflects creatinine production differences tied to muscle mass.
If your eGFR falls below 60, bring the result to your primary care provider rather than relying on this calculator alone — clinical staging requires urine albumin data too.
Track your eGFR over time rather than reacting to a single reading; trend matters more than any single number.
Avoid NSAIDs (ibuprofen, naproxen) for chronic pain if your eGFR is below 60, as they can further reduce kidney blood flow.
This tool is an educational estimate. A nephrologist's evaluation considers far more than creatinine and eGFR — do not use this calculator to self-diagnose CKD or adjust medications.
For most adults, an eGFR of 60 or above is generally considered normal function, per NKF guidelines. Many healthy younger adults will be above 90. eGFR naturally declines with age, so a reading of 65 in a healthy 75-year-old may be normal for their age.
eGFR stands for estimated glomerular filtration rate — the estimated rate at which your kidneys filter waste from the blood, measured in mL/min/1.73 m². The "e" indicates it's calculated from a creatinine blood test rather than measured directly.
Stage G3 is divided into G3a (eGFR 45–59, mild-to-moderate decrease) and G3b (eGFR 30–44, moderate-to-severe decrease). At G3b, NKF guidelines typically recommend nephrology referral and active management to slow progression.
Creatinine is a raw waste product your muscles produce; eGFR is the calculated estimate of how fast your kidneys clear it. A high creatinine means the kidneys aren't clearing it fast enough, which translates to a low eGFR. The two move in opposite directions.
Yes, especially in early CKD stages. Blood pressure control, blood sugar management in diabetics, reducing NSAID use, dietary sodium reduction, and stopping smoking are all evidence-backed strategies for slowing decline or stabilizing kidney function, per NKF recommendations.
The 2021 CKD-EPI update removed a race coefficient that was found to underestimate CKD severity in Black patients, leading to delayed care. The NKF and ASN jointly recommended the race-free version to ensure equitable CKD diagnosis and treatment.
No. CKD requires either an eGFR below 60 or evidence of kidney damage (elevated urine albumin, structural abnormalities) persisting for three or more months. A single low reading may reflect transient factors like dehydration or recent intense exercise.
Brief disclaimer: This calculator provides educational eGFR estimates using the 2021 CKD-EPI creatinine equation. Results are for informational purposes only and do not constitute medical diagnosis or treatment recommendations. CKD staging requires both eGFR and urine albumin data assessed clinically over three or more months. A single eGFR reading may reflect transient factors and should not be used to self-diagnose kidney disease. Always consult a nephrologist or primary care provider for interpretation of kidney function tests and personalized medical guidance.