CKD EPI Equations for Glomerular Filtration Rate (GFR)

This CKD EPI GFR calculator estimates kidney function for adults using the CKD EPI 2021 equations. It supports creatinine only (eGFRcr), cystatin C only (eGFRcys), and creatinine plus cystatin C (eGFRcr cys). Values are in mL per minute per 1.73 m².

The tool is built for doctors, nurses, and pharmacists who want a quick CKD EPI GFR estimate and a clear CKD stage for teaching and bedside talks.

CKD EPI 2021 GFR calculator · race free equation

CKD EPI GFR Inputs

Enter age, sex, and serum creatinine. Add cystatin C if you want the cystatin and combined equations. The calculator uses CKD EPI 2021 race free formulas.

years
Adult patients only. Use whole years.
The CKD EPI equation uses a factor for female sex.
mg/dL
Use a lab value that is IDMS aligned if possible.
The equation runs in mg/dL. The tool converts from µmol/L.
mg/L
Needed for eGFRcys and the combined CKD EPI equation.
All values show below. This pick just sets the main number and CKD stage.
Education use only. Check with lab and local rules.

This CKD EPI GFR calculator does not give medical advice. Always combine eGFR with urine tests, imaging, and full clinical review when you stage chronic kidney disease.

0 mL/min/1.73 m²
Main eGFR by CKD EPI
eGFRcr (creatinine) 0 mL/min/1.73 m²
eGFRcys (cystatin C) Need cystatin C
eGFRcr cys (combined) Need creatinine and cystatin C
CKD stage from main eGFR Not calculated
Serum creatinine in mg/dL 0.00
Cystatin C in mg/L 0.00
Age factor (0.9938^age) 0.000
Sex factor 1.000
eGFRcr = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^-1.200 × 0.9938^age × 1.012 if female
Main equation: eGFRcr Stage band: not set Creatinine unit: mg/dL Cystatin C: not used
CKD EPI equations estimate GFR. They are not exact measures. Use repeated tests, albuminuria, and clinical review before you label chronic kidney disease or change therapy.

What Is Glomerular Filtration Rate (GFR)

Glomerular Filtration Rate is the rate at which the kidneys filter blood through the glomeruli. For adults the normal range, adjusted to 1.73 m² body surface area, is roughly around 90 to 120 mL per minute in younger people and slowly falls with age. :contentReference[oaicite:0]{index=0}

GFR is central to chronic kidney disease staging. Current international guidelines use GFR categories from G1 to G5, where G1 means normal or high GFR and G5 means kidney failure. :contentReference[oaicite:1]{index=1}

In daily work we do not measure GFR directly. Instead we estimate it from blood tests. The CKD EPI equations are now the preferred way to estimate GFR in adults.

What Are CKD EPI Equations For GFR

CKD EPI stands for Chronic Kidney Disease Epidemiology Collaboration. This group built equations that estimate GFR from serum creatinine, cystatin C, or both. The 2021 CKD EPI creatinine equation uses age, sex, and creatinine but does not use race. :contentReference[oaicite:2]{index=2}

Equations on this page:

  • CKD EPI 2021 creatinine equation (eGFRcr).
  • CKD EPI 2021 cystatin C equation (eGFRcys).
  • CKD EPI 2021 creatinine plus cystatin C equation (eGFRcr cys).

All three give estimated GFR in mL per minute per 1.73 m². They are designed for adults with stable kidney function and standardized lab tests. :contentReference[oaicite:3]{index=3}

CKD EPI 2021 Creatinine Equation (eGFRcr)

The main CKD EPI 2021 creatinine equation is:

eGFRcr = 142 × min(Scr/κ, 1)α × max(Scr/κ, 1)-1.200 × 0.9938age × 1.012 (if female) :contentReference[oaicite:4]{index=4}

Where:

  • Scr is serum creatinine in mg/dL.
  • κ is 0.7 for females and 0.9 for males.
  • α is -0.241 for females and -0.302 for males.
  • min(Scr/κ, 1) means the smaller of Scr/κ or 1.
  • max(Scr/κ, 1) means the larger of Scr/κ or 1.

This 2021 version removes the race term that was used in the older 2009 CKD EPI equation. The change aims to avoid race based adjustments while keeping good accuracy for most adults. :contentReference[oaicite:5]{index=5}

CKD EPI 2021 Cystatin C And Combined Equations

Cystatin C is a small protein that is produced at a steady rate and cleared by the kidneys. It is less affected by muscle mass, so pairing cystatin C with creatinine can improve eGFR accuracy.

The 2021 CKD EPI cystatin C equation is: :contentReference[oaicite:6]{index=6}

eGFRcys = 133 × min(Scys/0.8, 1)-0.499 × max(Scys/0.8, 1)-1.328 × 0.996age × 0.932 (if female)

The 2021 combined creatinine plus cystatin C equation is:

eGFRcr cys = 135 × min(Scr/κ, 1)α × max(Scr/κ, 1)-0.544 × min(Scys/0.8, 1)-0.323 × max(Scys/0.8, 1)-0.778 × 0.9961age × 0.963 (if female) :contentReference[oaicite:7]{index=7}

Studies show that the combined equation can give tighter agreement with measured GFR than either marker alone, especially when kidney function is near the decision points for drug dosing or referral. :contentReference[oaicite:8]{index=8}

How This CKD EPI GFR Calculator Works

The CKD EPI calculator on this page follows the same steps as major clinical tools. Here is the workflow in simple terms.

  1. You enter age, sex, creatinine, and optional cystatin C.
  2. The tool converts creatinine from µmol/L to mg/dL if needed.
  3. It applies the CKD EPI 2021 creatinine equation to give eGFRcr.
  4. If you add cystatin C, it also computes eGFRcys and eGFRcr cys.
  5. It shows the main eGFR based on the equation you select in the drop down.
  6. The calculator then gives a CKD stage band based on that main eGFR value.

The result view shows raw eGFR numbers plus the age factor, sex factor, and a short stage label. This makes it easier to explain how CKD EPI equations use age and creatinine together.

CKD Staging From GFR Categories

Chronic kidney disease staging uses GFR categories G1 to G5. The calculator uses these cut points from current guideline tables. :contentReference[oaicite:9]{index=9}

  • G1: eGFR 90 or more, normal or high (needs kidney damage markers to call CKD).
  • G2: eGFR 60 to 89, mildly decreased.
  • G3a: eGFR 45 to 59, mild to moderate loss.
  • G3b: eGFR 30 to 44, moderate to severe loss.
  • G4: eGFR 15 to 29, severe loss.
  • G5: eGFR less than 15, kidney failure.

Remember that CKD is a long term state. You need at least three months of reduced eGFR or other kidney damage before you confirm chronic kidney disease. :contentReference[oaicite:10]{index=10}

How To Use CKD EPI GFR In Clinic

1. Screen and stage kidney disease

Use CKD EPI GFR together with urine albumin to screen high risk groups such as people with diabetes, high blood pressure, and cardiovascular disease. GFR stage and albumin category together give risk level for kidney failure and heart events. :contentReference[oaicite:11]{index=11}

2. Adjust drug dosing

Many drugs need dose change at low kidney function. Some labels still quote Creatinine Clearance by Cockcroft Gault, but others now accept CKD EPI eGFR. Always check the drug monograph and your local renal dosing guide.

3. Plan referral and follow up

People with eGFR in G3b, G4, or G5 often need closer follow up and may need referral to nephrology, depending on age, albumin leak, and comorbid risk. :contentReference[oaicite:12]{index=12}

4. Track change over time

A single eGFR is less useful than a trend. Use the CKD EPI calculator alongside lab reports to see if GFR is stable, slowly dropping, or falling fast. A sustained large drop in eGFR may signal rapid CKD progression and should trigger review. :contentReference[oaicite:13]{index=13}

Limitations Of CKD EPI Equations

No GFR equation is perfect. The CKD EPI 2021 equations improve on older formulas but still have limits. :contentReference[oaicite:14]{index=14}

  • They assume stable kidney function, not acute kidney injury.
  • They work best when lab creatinine and cystatin C are standardized.
  • They may be less accurate at extremes of body size or diet.
  • They are developed for adults and should not be used for children.
  • Different labs and platforms may still show small systematic shifts.

Because of these limits many experts suggest confirming eGFR with a cystatin C based equation when treatment decisions depend on small differences in GFR. :contentReference[oaicite:15]{index=15}

Frequently Asked Questions About This CKD EPI GFR Calculator

Is this CKD EPI calculator based on the 2021 race free equation

Yes. The creatinine part uses the CKD EPI 2021 equation that does not include race. It uses age, sex, and standardized serum creatinine. :contentReference[oaicite:16]{index=16}

Should I use eGFRcr, eGFRcys, or eGFRcr cys

Many centers start with eGFRcr because creatinine is widely available. When results are borderline or when muscle mass is very low or very high, cystatin C or the combined equation can give a better estimate. :contentReference[oaicite:17]{index=17}

Can I use this calculator for dialysis patients

No. In people who need dialysis or who have very low kidney function, measured clearance and specialist advice should guide management. eGFR equations are not reliable in that setting. :contentReference[oaicite:18]{index=18}

Is CKD EPI better than MDRD for higher GFR

Yes. Studies show that CKD EPI has less bias and better accuracy than the MDRD equation at GFR above 60, which helps avoid over calling CKD in people with near normal function. :contentReference[oaicite:19]{index=19}

Does this calculator replace lab reported eGFR

No. It mirrors the same equations many labs now use and is helpful for education and planning. Always read and use the official eGFR value that appears on the lab report for your final decisions.

Start Using The CKD EPI Equations For GFR

Enter age, sex, creatinine, and optional cystatin C into the CKD EPI GFR calculator at the top of this page. Choose which equation you want to highlight and review the CKD stage label. Use the results as a clean, simple way to talk about kidney function with patients, learners, and your care team, while still following full guidelines and local rules.