eGFR Calculator (CKD‑EPI)

Use the eGFR Calculator

Estimate kidney function with the eGFR calculator using the CKD‑EPI 2021 equation. Enter age, sex, and creatinine in mg/dL or µmol/L. This kidney function calculator reports eGFR (mL/min/1.73 m²), optional absolute GFR, and CKD stage in a clean summary.

How to Use eGFR Calculator (CKD‑EPI)

1. Step 1: Enter age and sex

   Type your age in years (18–120) and select sex. The CKD‑EPI 2021 equation adjusts for these.

2. Step 2: Add creatinine and pick units

   Enter your serum creatinine and select mg/dL or µmol/L. We convert automatically if you switch units.

3. Step 3: Optionally adjust for body size

   Toggle the BSA adjustment to enter height and weight and see absolute GFR (mL/min) alongside the indexed eGFR.

4. Step 4: Calculate eGFR

   Tap Calculate to get eGFR (mL/min/1.73 m²), absolute GFR if enabled, and CKD stage (G1–G5).

5. Step 5: Review and explore

   Compare with CKD ranges. Use Related Calculators to dig deeper or convert units as needed.

Key Features

• CKD‑EPI 2021 eGFR (no race)
• CKD staging (G1–G5)
• Creatinine units: mg/dL & µmol/L
• Optional BSA‑adjusted absolute GFR
• Mobile‑first inputs, sticky results

Understanding Results

eGFR Calculator: what your number means

Use the result from the eGFR calculator as a snapshot of filtration, not a diagnosis. A value ≥ 90 is often normal in the absence of kidney damage. Results between 60–89 can be normal for some people, especially with age; persistent reduction and other findings guide staging. Always interpret trends and clinical context with a clinician.

Formula

This tool uses the CKD‑EPI 2021 creatinine equation. In plain English, it compares your creatinine to a sex‑specific reference value and then adjusts for age. The core terms are min(Scr/k, 1) and max(Scr/k, 1), where Scr is your serum creatinine and k is 0.7 for females or 0.9 for males. The exponents differ slightly by sex. A small age factor (0.9938 per year) gradually lowers eGFR with age. The final value is expressed as mL/min per 1.73 m² (standardized body surface area).

Reference Ranges & Interpretation

Common CKD stages use these cutoffs: G1 ≥ 90 (normal or high when no kidney damage), G2 60–89 (mildly decreased), G3a 45–59, G3b 30–44, G4 15–29, G5 < 15 mL/min/1.73 m². One isolated result is only a snapshot. Clinicians usually confirm chronicity (≥ 3 months) and consider albuminuria, imaging, and risk factors. In general, lower eGFR suggests reduced filtering capacity and warrants follow‑up if persistent.

Assumptions & Limitations

eGFR is an estimate based on population data; it is not a direct measurement. Creatinine reflects muscle metabolism, so non‑kidney factors (large muscle mass, very low muscle mass, high meat intake, intense exercise, pregnancy, and certain medications) can shift creatinine and the derived eGFR. The CKD‑EPI 2021 equation removes a race factor used previously, but special situations may still need cystatin C or measured clearance. Results here are informational only.

Clinical context & follow‑up

eGFR trends over time are often more meaningful than a single value. If a result is lower than expected, many clinicians will repeat labs, confirm units, and review medications, hydration, and recent exercise. When persistent reduction is suspected, albumin‑to‑creatinine ratio (ACR), blood pressure, and imaging can clarify risk and guide next steps.

At body‑size extremes, adjusting to absolute GFR (mL/min) can be useful when dosing medications. Use the BSA toggle in this eGFR calculator when you have height and weight available. Discuss dosing decisions with your clinician—this page is for planning and education, not medical advice.

Complete Guide: eGFR Calculator (CKD‑EPI)

Estimate kidney function with the eGFR calculator using the CKD‑EPI 2021 formula. Enter age, sex, and creatinine (mg/dL or µmol/L) to get eGFR and CKD stage.

The goal is simple: make it fast and clear to estimate kidney function using the CKD‑EPI 2021 equation, then help you read the number in context. This guide explains how eGFR Calculator (CKD‑EPI) works, why units matter, how clinicians interpret the result, and what to consider next.

What is eGFR?

Estimated glomerular filtration rate (eGFR) is a calculated value that approximates how well your kidneys filter blood. Because precisely measuring filtration requires specialized testing, most labs report an estimate based on common blood markers—usually serum creatinine—and demographic factors like age and sex. The number is standardized to a body surface area of 1.73 m² and expressed as mL/min/1.73 m².

Clinicians pair eGFR with other information—such as urine albumin, imaging, history, and medications—to evaluate kidney health. A single result provides a snapshot; chronic kidney disease typically requires evidence that changes persist for three months or more. For day‑to‑day use, the egfr calculator (ckd‑epi) helps you quickly estimate where you might fall in CKD staging and whether further discussion with your clinician could be appropriate.

Which formula does this tool use?

This tool uses the CKD‑EPI 2021 creatinine equation, which removed the race coefficient seen in earlier versions. The formula compares your creatinine to a sex‑specific threshold (0.7 for females, 0.9 for males), applies two power terms, and adjusts for age. In practice, the math compresses several risk factors into one practical estimate that tracks with kidney filtering capacity for most adults.

While creatinine is convenient, it comes from muscle metabolism and can be influenced by muscle mass, recent exercise, or a large meat meal. When precision matters, clinicians may confirm with cystatin C or a measured clearance study. Still, CKD‑EPI 2021 remains the most common starting point in primary care for adults.

Creatinine units and conversion

Labs report serum creatinine in either mg/dL (commonly in the U.S.) or µmol/L (international). The two are convertible: 1 mg/dL ≈ 88.4 µmol/L. If your report uses µmol/L, select µmol/L in the calculator; if it uses mg/dL, keep the default. Switching units in the tool automatically converts your entered value so you can compare results in a format you recognize.

How CKD staging works

eGFR is grouped into stages G1 to G5. As a quick reference: G1 is ≥ 90 (normal/high when no damage), G2 is 60–89, G3a is 45–59, G3b is 30–44, G4 is 15–29, and G5 is < 15 mL/min/1.73 m². Staging is only part of the picture; clinicians also consider albuminuria, imaging, comorbidities, and the persistence of findings over time. That’s why your doctor may repeat tests to confirm a trend rather than relying on one draw.

If your eGFR is borderline or fluctuates, keep the bigger view in mind: hydration, recent diet, lab timing, and short‑term illness can nudge creatinine and therefore eGFR. Trends and clinical context matter more than a single number.

eGFR vs. creatinine clearance

eGFR is an estimate designed to reflect overall kidney filtration. Creatinine clearance (CrCl), often calculated with the Cockcroft–Gault equation, is another estimate used frequently for medication dosing. The two numbers can differ, especially in people with unusual body size or muscle mass. If you need a CrCl estimate for dosing, try our creatinine clearance calculator after you check eGFR here.

Indexed vs. absolute GFR (BSA)

By convention, eGFR is indexed to a body surface area (BSA) of 1.73 m². That standardization makes results easier to compare across people, but it can obscure real‑world differences at body‑size extremes. Our calculator can show an absolute GFR (mL/min) by adjusting eGFR to your estimated BSA (Du Bois formula). This adjustment is optional and mainly useful when body size is far from average.

If you want a full BSA estimate on its own, use the BSA calculator to compare methods and see how small changes in height or weight influence BSA.

Factors that affect accuracy

Because creatinine reflects muscle metabolism, non‑kidney factors can shift it. High muscle mass, a heavy workout, or a large meat meal can transiently raise creatinine and lower calculated eGFR. Very low muscle mass—such as frailty—can do the opposite. Dehydration, some medications, and lab timing also contribute to day‑to‑day variation. Persistent patterns across time carry more weight than a single lab.

When values are discordant with the clinical picture, clinicians may confirm kidney function with cystatin C or a measured clearance test. This is common in cases where medication dosing hinges on precise kidney function and creatinine‑based estimates seem unreliable.

Special situations

Some scenarios require extra caution when interpreting eGFR: pregnancy, acute kidney injury, rapidly changing creatinine, extremes of muscle mass, severe liver disease, or rare conditions affecting creatinine production. Pediatric estimates use different equations (e.g., Schwartz), and are outside the scope of this adult‑focused tool. If any of these apply, your clinician may opt for alternate markers or direct measurements.

Tracking eGFR trends over time

One number rarely tells the whole story. Check that creatinine was measured in similar conditions (hydration, time of day, lab) and compare several results across months. A gentle, stable eGFR with low urine albumin is different from a downward trend or persistent albuminuria at the same eGFR. Use this eGFR calculator to understand today’s result, then review trends with your clinician to decide on next steps such as blood pressure targets, medication review, or nephrology referral.

What to do next

If your result is new or unexpected, consider repeating it after routine conditions—hydration, sleep, usual diet—are stable. Bring a copy to your next appointment and discuss the broader context: blood pressure, diabetes status, medications, and any symptoms. If you monitor glucose, our A1C calculator can convert between A1C and eAG for a fuller metabolic picture, and our blood pressure calculator helps you track cardiovascular risk alongside kidney health.

For medication dosing, many labels still reference creatinine clearance (CrCl) rather than eGFR. If you’re adjusting a drug with renal dosing, confirm whether the recommendation uses CrCl and, if so, compute it with the creatinine clearance calculator. Share both values (eGFR and CrCl) with your clinician—this avoids talking past each other and helps land on the safest dose.

Hydration also matters: dehydration can raise creatinine temporarily. If you want a quick sense of daily fluid targets, try our hydration calculator. And if you’re reviewing kidney‑related lab markers as a set, our kidney function calculator provides a useful companion view.

Helpful related calculators

• Creatinine clearance (CrCl) — often used for medication dosing when a drug label specifies CrCl.
• Body surface area (BSA) — explore indexed vs. absolute GFR by adjusting for body size.
• A1C ↔ eAG — review glucose patterns that often coexist with kidney considerations.
• Blood pressure — hypertension management is central to kidney health.
• Hydration — a practical check on fluid targets.

References and further reading

For clinical background and patient‑friendly education, see:

Reporting units, rounding, and lab quirks

Lab reports can look different even when they reflect the same underlying calculation. Some labs round eGFR to whole numbers, others report one decimal, and pediatric panels may default to different reference ranges. Creatinine units (mg/dL vs µmol/L) also change the inputs you enter here, but not the idea: the eGFR calculator standardizes the math so you can compare results across time. When numbers seem inconsistent, check whether tests were done under similar conditions (hydration, time of day) and whether the lab switched reporting formats. Bring the full report to your next visit so your clinician can see the context, not just the final figure.

• National Kidney Foundation: GFR
• NCBI Bookshelf: Chronic Kidney Disease (overview)

This article is informational and does not provide medical advice. Always discuss lab results and treatment decisions with your clinician.

Frequently Asked Questions