CKD-EPI equations estimate GFR from standardised serum creatinine and/or cystatin C in adults with stable kidney function. This calculator implements the 2021 race-free CKD-EPI equations for creatinine and creatinine–cystatin C, plus the 2012 CKD-EPI cystatin C equation.

Equation	Biomarkers	Evidence base	Use notes
2021 CKD-EPI creatinine	Creatinine, age, sex	Derived from 10 pooled studies with measured GFR and validated in 12 external studies.	Race-free refit of the 2009 creatinine equation. KDIGO 2024 favours race-free CKD-EPI equations over MDRD for routine adult eGFR reporting.
2012 CKD-EPI cystatin C	Cystatin C, age, sex	Derived from 13 studies including 5352 adults with measured GFR.	Less influenced by muscle mass than creatinine, though inflammation, thyroid disease and corticosteroid therapy can affect cystatin C.
2021 CKD-EPI creatinine–cystatin C	Creatinine, cystatin C, age, sex	Developed using pooled measured-GFR data and externally validated.	Usually the most accurate option when both assays are available, especially near drug dosing, contrast or transplant thresholds.

Practical limitations

Use in adults aged 18 years or older with stable kidney function and standardised assays. These equations are less reliable in acute kidney injury, pregnancy, extremes of body size or muscle mass and some critical care settings. Measured GFR or specialist nephrology advice may be preferable.

KDIGO CKD prognosis uses GFR categories G1 to G5 together with albuminuria categories A1 to A3 and persistence over 3 months or longer. G1 to G2 alone do not fulfil CKD criteria without other markers of kidney damage.

KDIGO 2024 recommends confirmatory testing with cystatin C or the combined eGFRcr-cys equation when eGFRcr is 45 to 59 mL/min/1.73 m² with normal albumin excretion, or when creatinine may be an unreliable marker.

CKD-EPI Equations for Glomerular Filtration Rate (GFR)