eGFR Calculator (CKD-EPI 2021)

Methodology

CKD-EPI 2021 creatinine equation (race-free)

142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^age × 1.012 [female]; κ = 0.7 (F) / 0.9 (M); α = −0.241 (F) / −0.302 (M)

KDIGO 2024 recommends a validated estimating equation; the 2021 race-free CKD-EPI creatinine equation is one, recommended for use in the US by the NKF–ASN task force. GFR categories G1–G5 follow KDIGO.

Who it is for

Adults aged 18 and over with a stable creatinine level.

Version

2.0.1

How this calculator works

Where the formula comes from

• The 2021 CKD-EPI equations were published by Inker and colleagues in the New England Journal of Medicine: one uses serum creatinine alone and one uses creatinine plus cystatin C, and neither uses race.^[1]
• The creatinine equation was developed in 8,254 participants from 10 studies (31.5% Black) and validated in 4,050 participants from 12 other studies, against measured GFR.^[1]
• The first CKD-EPI creatinine equation (2009) included a coefficient for Black race; the 2021 equation removed it and recalibrated the other terms.^[2][1]

The inputs

• The equation uses standardised serum creatinine (mg/dL), age in years and sex; it does not use race.^[1]
• Sex sets the constants: κ is 0.7 for women and 0.9 for men, α is −0.241 for women and −0.302 for men, and the result is multiplied by 1.012 for women.^[1]
• Sex is included because average creatinine generation differs between women and men.^[1]
• The result is expressed in mL/min per 1.73 m² of body surface area.^[1]

Versions and alternatives

• In the 2021 study, the equation combining creatinine and cystatin C was more accurate than the creatinine-only equation.^[1]
• The 2009 CKD-EPI creatinine equation was more accurate than the MDRD Study equation, particularly at higher GFR values.^[2]
• The European Kidney Function Consortium (EKFC) equation is an alternative creatinine-based equation developed in European populations.^[3]

Where accuracy falls (published evidence)

• Creatinine-based estimates are less accurate when muscle mass is unusual, for example in people with amputations, very high muscle mass or frailty.^[3]
• Creatinine-based eGFR is unreliable when serum creatinine is not at steady state, as in acute kidney injury, and the standard adult equations are not validated in pregnancy.^[3]
• Diet can change serum creatinine, and KDIGO advises considering dietary intake when interpreting it.^[3]
• The equations were developed and validated mainly in populations from the United States and Europe, and their accuracy may differ in other populations.^[1]

What guidelines say

• KDIGO 2024 recommends estimating GFR with a validated equation rather than relying on serum creatinine alone.^[3]
• KDIGO 2024 recommends adding cystatin C (the combined creatinine–cystatin C equation) when the creatinine-based estimate is less accurate and GFR affects clinical decisions.^[3]
• KDIGO 2024 states that race should not be used in the computation of eGFR, and a US task force (NKF–ASN) recommended adopting the 2021 race-free CKD-EPI creatinine equation.^[3][4]
• KDIGO 2024 advises using the same validated equation consistently within a geographical region.^[3]
• KDIGO defines chronic kidney disease as abnormal kidney structure or function, with implications for health, present for at least three months; an eGFR in the G1 or G2 range alone does not establish CKD without other markers of kidney damage.^[3]

Sources

1. Inker LA, Eneanya ND, Coresh J, et al. New creatinine- and cystatin C-based equations to estimate GFR without race. N Engl J Med. 2021;385(19):1737–1749. doi:10.1056/NEJMoa2102953
2. Levey AS, Stevens LA, Schmid CH, et al. A new equation to estimate glomerular filtration rate. Ann Intern Med. 2009;150(9):604–612. doi:10.7326/0003-4819-150-9-200905050-00006
3. Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2024 clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney Int. 2024;105(4S):S117–S314. doi:10.1016/j.kint.2023.10.018
4. Delgado C, Baweja M, Crews DC, et al. A unifying approach for GFR estimation: recommendations of the NKF-ASN Task Force on reassessing the inclusion of race in diagnosing kidney disease. Am J Kidney Dis. 2022;79(2):268–288. doi:10.1053/j.ajkd.2021.08.003

Compiled from the published sources above. Every statement was agreed independently by three AI research tools (Claude, ChatGPT, DeepSeek) and its source verified in PubMed or Crossref by the Hakeemly editorial team. Not reviewed by a doctor unless stated. Agreed on 2026-10-11

Worked example: how to calculate eGFR

Calculation:

142 × (1/0.9)^−1.2 × 0.9938^50 = 142 × 0.8812 × 0.7329 = 91.7

An illustration with sample values, worked out with the same method the tool above uses.

Limitations

• A G1 or G2 value alone does not mean kidney disease: CKD also needs markers such as albumin in the urine, lasting more than 3 months.
• Less accurate with unusual muscle mass (bodybuilders, amputations, frailty), vegetarian diets, pregnancy and acute kidney injury.

References

1. Inker LA, Eneanya ND, Coresh J, et al. New creatinine- and cystatin C-based equations to estimate GFR without race. N Engl J Med. 2021;385(19):1737–1749. doi:10.1056/NEJMoa2102953
2. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int. 2024;105(4S):S117–S314. doi:10.1016/j.kint.2023.10.018