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How to Calculate eGFR

CKD-EPI 2021 (race-free) from serum creatinine, a full worked example, MDRD vs Cockcroft-Gault, cystatin C, and KDIGO stages — explained step by step.

Published: 18 August 2026 · ~9 min read
Written by Dr. Emily Carter, PharmD, BCPS · Medically reviewed

How to Calculate eGFR

To calculate eGFR from serum creatinine, use the race-free CKD-EPI 2021 equation published by Inker et al. and endorsed by the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN): eGFR = 142 × min(SCr/κ,1)α × max(SCr/κ,1)−1.200 × 0.9938Age × 1.012 if female. Report the result in mL/min/1.73 m². Prefer our free eGFR calculator for the arithmetic.

Serum creatinine → eGFR result

How is eGFR calculated from a blood test.

eGFR stages of kidney disease

KDIGO GFR categories (mL/min/1.73 m²).

What you need to calculate eGFR

What numbers do you need to calculate eGFR? For the adult eGFR calculation from serum creatinine you need:

  • Serum creatinine from an eGFR blood test (stable, not rising in AKI)
  • Age in years (CKD-EPI 2021 is validated in adults)
  • Sex (the eGFR formula variables include separate κ and α for female vs male)

You do not need weight, height, or race for the eGFR race-free formula. Optional: cystatin C when muscle mass is unusual. Urea (BUN) is not part of CKD-EPI 2021; how to calculate eGFR from creatinine and urea is a different (older) approach and is not the current NKF standard.

If the lab reports creatinine in µmol/L, complete creatinine unit conversion for eGFR first: mg/dL = µmol/L ÷ 88.4. Use our creatinine unit converter if you prefer not to convert by hand.

What is the eGFR formula?

The CKD-EPI formula explained for current adult reporting is the CKD-EPI 2021 equation (creatinine). It is an eGFR without race calculation. The result is eGFR mL/min/1.73 m² explained as filtration indexed to a standard 1.73 m² body surface area — not an individualised mL/min clearance.

CKD-EPI 2021 creatinine race-free · mg/dL
eGFR = 142 × min(SCr/κ,1)α × max(SCr/κ,1)−1.200 × 0.9938Age × 1.012if female
κ = 0.7 (female) / 0.9 (male). α = −0.241 (female) / −0.302 (male). SCr in mg/dL. Source: Inker LA et al.; NKF–ASN 2021 race-free recommendation.

Calculate eGFR step by step

This is the eGFR calculation step by step for how to calculate eGFR using CKD-EPI equation by hand.

  1. Step 1 — Collect the eGFR test inputs. Age (years), sex, and a recent stable serum creatinine from the blood test.
  2. Step 2 — Convert units (eGFR calculation mg/dL vs µmol/L). If creatinine is in µmol/L, divide by 88.4 to get mg/dL.
  3. Step 3 — Set κ and α for female vs male. Female: κ = 0.7, α = −0.241. Male: κ = 0.9, α = −0.302.
  4. Step 4 — Compute SCr/κ. Divide serum creatinine (mg/dL) by κ.
  5. Step 5 — Apply the min and max terms. min(SCr/κ, 1)α and max(SCr/κ, 1)−1.200.
  6. Step 6 — Multiply by 142, age, and the female factor. × 0.9938Age, then × 1.012 if female.
  7. Step 7 — Report the eGFR value. Round to a whole number in mL/min/1.73 m² and map to a KDIGO G-stage if the creatinine is stable.

Can I calculate eGFR myself? Yes — but the exponents make hand math easy to get wrong. Calculate your eGFR instantly with the same CKD-EPI 2021 equation.

Worked example: eGFR value

Case: 65-year-old woman, serum creatinine 1.1 mg/dL (how to calculate eGFR for female vs male uses different κ and α).

CKD-EPI 2021 worked example (female, SCr 1.1 mg/dL, age 65)
StepCalculationResult
κ and αFemale constants0.7 and −0.241
SCr/κ1.1 ÷ 0.71.571
min(SCr/κ, 1)αmin(1.571, 1)−0.2411.000
max(SCr/κ, 1)−1.2001.571−1.2000.581
0.9938Age0.9938650.667
Female factor× 1.0121.012
eGFR142 × 1 × 0.581 × 0.667 × 1.01256 mL/min/1.73 m²

The eGFR value is 56 mL/min/1.73 m² (KDIGO G3a if persistent). For how to calculate eGFR for male / how to calculate eGFR in male with the same age and creatinine, use κ = 0.9, α = −0.302, and omit the 1.012 factor.

MDRD vs CKD-EPI in adults

The MDRD formula explained (IDMS-traceable 4-variable) is a legacy adult equation still seen on older reports:

MDRD 4-variable (IDMS) legacy · optional race
eGFR = 175 × SCr−1.154 × Age−0.203 × 0.742if female × 1.212if Black, optional
Levey 2006. NKF–ASN now prefer CKD-EPI 2021 without a race coefficient. Compare on the MDRD GFR calculator.

CKD-EPI vs MDRD formula: use CKD-EPI 2021 for current staging language. Use MDRD only to match an older printout. Do not mix them when tracking an eGFR baseline for monitoring or an eGFR decline rate over time — keep the same equation.

How to calculate eGFR with cystatin C

The cystatin C eGFR formula (CKD-EPI 2012 cystatin-only, and CKD-EPI 2021 creatinine–cystatin combined) is useful when muscle mass skews creatinine. How to calculate eGFR with cystatin C still needs age and sex; it does not use race in the 2021 combined equation. Enter both markers on the eGFR calculator rather than mixing equations by hand.

eGFR vs creatinine clearance

How to calculate eGFR using Cockcroft-Gault formula is a common mix-up. Cockcroft-Gault estimates creatinine clearance (CrCl) in mL/min, not BSA-indexed eGFR. How to calculate eGFR from creatinine clearance, how to calculate CrCl from eGFR, and how to calculate creatinine clearance from eGFR have no exact conversion. You may de-index eGFR as GFR (mL/min) = eGFR × (BSA ÷ 1.73), but that is still not Cockcroft-Gault.

eGFR vs CrCl for kidney function assessment
Feature eGFR (CKD-EPI 2021) CrCl (Cockcroft-Gault)
Unit mL/min/1.73 m² mL/min
Inputs Creatinine, age, sex Creatinine, age, sex, weight
Best for CKD staging, lab reports Many drug-dosing labels
Race coefficient None (2021) None

For CrCl dosing math see the creatinine clearance calculator and CKD-EPI vs Cockcroft-Gault.

eGFR in CKD stages

After you calculate eGFR, map a stable result to KDIGO G1–G5 (chart above). A single low number after illness is not automatic CKD. For how to calculate eGFR in elderly patients, use the same CKD-EPI 2021 equation — age is already in the formula — but interpret sarcopenia carefully (creatinine can look “too good”).

How do you calculate kidney function for monitoring? Pick one equation (usually CKD-EPI 2021), record an eGFR baseline for monitoring, and compare later values with the same method. Do not switch between MDRD and CKD-EPI when judging decline.

eGFR FAQ

What is the eGFR formula?

CKD-EPI 2021 (NKF–ASN): eGFR = 142 × min(SCr/κ,1)α × max(SCr/κ,1)−1.200 × 0.9938Age × 1.012 if female. SCr in mg/dL. Result in mL/min/1.73 m².

What numbers do you need to calculate eGFR?

Serum creatinine, age, and sex. Weight is not required for CKD-EPI. Convert µmol/L to mg/dL (÷ 88.4) first.

Can I calculate eGFR myself?

Yes, with the steps above, or how to calculate eGFR online with a free calculator. Confirm against the lab report for clinical use.

How accurate is eGFR calculation?

CKD-EPI 2021 is the preferred adult creatinine equation in current NKF–ASN guidance, but it is still an estimate. AKI, extremes of muscle mass, and non-adults reduce accuracy.

How do you calculate creatinine clearance from eGFR?

There is no exact conversion. Calculate Cockcroft-Gault CrCl separately, or de-index eGFR with BSA only as an illustration — not as a substitute for a CrCl-labeled dose.

How do you calculate eGFR for female vs male?

Female: κ = 0.7, α = −0.241, × 1.012. Male: κ = 0.9, α = −0.302, no extra multiplier.

How to compute eGFR with a calculator?

Use the eGFR calculator (CKD-EPI 2021 default, optional cystatin and MDRD). For unit conversion use the creatinine unit converter.

Medically Reviewed By

Dr. Emily Carter, PharmD, BCPS
Dr. Emily Carter, PharmD, BCPS
Board-Certified Clinical Pharmacist · Nephrology & Internal Medicine

Reviewed for CKD-EPI 2021 / NKF–ASN equation accuracy, unit handling, and clear staging vs dosing language. View full author profile.

Educational only — not medical advice. Confirm dosing and staging against current labels, laboratory methods, and local protocols. See our Disclaimer.