Creatinine only
Male coefficient, age 50, creatinine 1.2 mg/dL → raw eGFRcr ≈ 73.6735 → displayed 74 mL/min/1.73 m², G2 numerical range.
Educational reference only. Not a diagnostic tool. See full disclaimer.
NephrologyeGFR
Adult eGFR Calculator
Estimate adult race-free indexed glomerular filtration rate (eGFR) with 2021 CKD-EPI creatinine, 2012 cystatin C, or 2021 combined equations.
Content updated: View sources
QuickMedCalc is developed and maintained by an independent developer. Medical content is not independently reviewed by a physician.
Formula and medical content are based on the references listed on this page. See sources, About, and Sources and Review Process.
About
This adult calculator implements three indexed GFR estimates: 2021 CKD-EPI creatinine (eGFRcr), 2012 CKD-EPI cystatin C (eGFRcys), and 2021 CKD-EPI creatinine–cystatin C (eGFRcr-cys). The 2021 equations are race-free; this page does not request race or calculate the historical 2009 race coefficient. [1, 12]
Creatinine alone displays eGFRcr, cystatin C alone displays eGFRcys, and paired values display all three estimates with eGFRcr-cys as the primary result. Pairing is required so the combined equation does not silently mix biomarkers from unrelated clinical time points. The combined equation is generally more accurate than creatinine alone, while the single-marker values remain useful when one marker has an important non-GFR determinant. [1, 7]
Every result is an estimate indexed to 1.73 m², not measured GFR. It does not by itself diagnose CKD or decide a medicine dose, referral, dialysis, or transplant assessment. [5, 9]
Formula
2021 CKD-EPI eGFRcr: 142 × min(SCr/κ,1)^α × max(SCr/κ,1)^−1.200 × 0.9938^age × 1.012 if female (female: κ 0.7, α −0.241; male: κ 0.9, α −0.302). [1, 6]
2012 CKD-EPI eGFRcys: 133 × min(Scys/0.8,1)^−0.499 × max(Scys/0.8,1)^−1.328 × 0.996^age × 0.932 if female. [2, 3, 6]
Interpretation
| G range | Displayed primary eGFR |
|---|---|
| G1 numerical range | ≥90 mL/min/1.73 m² |
| G2 numerical range | 60–89 mL/min/1.73 m² |
| G3a numerical range | 45–59 mL/min/1.73 m² |
| G3b numerical range | 30–44 mL/min/1.73 m² |
| G4 numerical range | 15–29 mL/min/1.73 m² |
| G5 numerical range | <15 mL/min/1.73 m² |
These are G numerical ranges, not stand-alone diagnoses. A single low eGFR cannot diagnose CKD. CKD requires abnormalities of kidney structure or function—including reduced GFR or markers of kidney damage—to be present for at least 3 months. G1 or G2 does not establish CKD without persistent evidence of kidney damage. Assessment also considers urine ACR/albuminuria, cause, trend, and clinical context. [5]
This calculator does not convert a G range into treatment, referral, dosing, dialysis, or transplant instructions.
How this calculator selects an equation
- Creatinine only: 2021 CKD-EPI eGFRcr.
- Cystatin C only: 2012 CKD-EPI eGFRcys.
- Both markers from the same specimen or a reasonably paired time point: 2021 CKD-EPI eGFRcr-cys is primary, followed by eGFRcr and eGFRcys.
This is fixed implementation logic, not an individualized claim that one model is best for a particular person. [6, 7]
Inputs, assays, and units
Serum creatinine may be entered in mg/dL or µmol/L; µmol/L is divided by 88.4 before calculation. Cystatin C is entered in mg/L. [4] The published equations are intended for IDMS-traceable creatinine and IFCC-standardized cystatin C. [6, 7]
The calculator does not round either biomarker before applying an equation. Changing the creatinine unit clears the value to prevent the same digits from being silently reinterpreted in a different unit; that clearing behavior is a software safeguard, not a medical rule.
CKiD U25 is intended for people ages 1–25 with mild-to-moderate CKD; it is not a general screening equation for all asymptomatic adults ages 18–25. This page calculates only the adult CKD-EPI models and does not replace pediatric or young-adult CKD-specific assessment. [6, 8]
Rounding and the displayed G range
This implementation keeps the formula result at full floating-point precision, rounds only the final displayed eGFR to the nearest whole number, and assigns the visible G numerical range from that displayed integer. A positive raw estimate that rounds below 1 is shown as <1 and lies in the G5 numerical range. Input-validation boundaries are software safety limits, not healthy ranges or laboratory reference intervals.
Worked examples
Cystatin C only
Male coefficient, age 50, cystatin C 1.0 mg/L → raw eGFRcys ≈ 80.9323 → displayed 81 mL/min/1.73 m², G2 numerical range.
Paired biomarkers
Male coefficient, age 50, creatinine 1.0 mg/dL and cystatin C 1.0 mg/L → raw combined eGFRcr-cys ≈ 88.1440 → primary display 88 mL/min/1.73 m², G2 numerical range. The two single-marker estimates also remain visible.
Creatinine unit equivalence
Creatinine 1.0 mg/dL and 88.4 µmol/L normalize to the same value and produce the same unrounded eGFRcr when age and coefficient are unchanged.
These examples demonstrate the implemented arithmetic and display sequence; they are not patient interpretations. Formula identities come from the published CKD-EPI equations. [1, 2, 6]
Indexed versus nonindexed eGFR
This page reports mL/min/1.73 m². A mathematical conversion sometimes used to remove body-surface-area indexing is: nonindexed eGFR = indexed eGFR × BSA ÷ 1.73. This page does not collect BSA or perform that conversion. [9]
Drug labels and applicable protocols can specify different kidney-function measures, equations, or cut points; the FDA does not require one estimating equation for every medicine. This calculator does not choose a medicine or dose. [9, 10]
When estimates may be less reliable
- AKI or rapidly changing creatinine can violate the steady-state assumption.
- Creatinine can be influenced by extreme muscle mass, bodybuilding, amputation, spinal cord injury, frailty, malnutrition, muscle-wasting disease, creatine supplements, diet, tubular secretion, and some medicines.
- Cystatin C can have non-GFR associations with inflammation, smoking, obesity, thyroid status, glucocorticoids, cancer, high cell turnover, heart failure, cirrhosis, and other clinical states.
- If both biomarkers have important non-GFR determinants, the combined estimate can also be inaccurate.
- These adult equations are not valid for pregnancy. [11]
Higher GFR estimates are generally less precise, and a trend calculated with the same equation is often more informative than an isolated value. Accuracy-critical or high-risk decisions can require measured GFR rather than another estimating equation. [5, 7, 9]
eGFR is one part of kidney assessment
A complete kidney assessment may combine eGFR with urine ACR or other albuminuria evidence, duration of abnormalities, likely cause, serial trend, and the wider clinical context. This page does not create a separate CKD stage or risk algorithm from those factors. [5, 7]
References
- Inker LA, et al. New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race. N Engl J Med. 2021;385(19):1737–1749. PMID 34554658. DOI 10.1056/NEJMoa2102953.
- Inker LA, et al. Estimating Glomerular Filtration Rate from Serum Creatinine and Cystatin C. N Engl J Med. 2012;367(1):20–29. PMID 22762315. DOI 10.1056/NEJMoa1114248.
- Inker LA, et al. Estimating Glomerular Filtration Rate from Serum Creatinine and Cystatin C. Formula correction. N Engl J Med. 2012;367:681. DOI 10.1056/NEJMx120052.
- Inker LA, et al. Estimating Glomerular Filtration Rate from Serum Creatinine and Cystatin C. Cystatin C unit correction. N Engl J Med. 2012;367:2060. DOI 10.1056/NEJMx120062.
- KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease.
- NIDDK. eGFR Equations for Adults.
- NIDDK. Glomerular Filtration Rate Equations: equation selection, reporting, standardization, and limitations.
- NIDDK. eGFR Equations for Children, Adolescents, and Young Adults, including CKiD U25.
- NIDDK. Determining Drug Dosing in Adults with Chronic Kidney Disease.
- FDA. Pharmacokinetics in Patients with Impaired Renal Function — Study Design, Data Analysis, and Impact on Dosing. Guidance for Industry. March 2024.
- Wiles K, et al. Clinical practice guideline on pregnancy and renal disease. BMC Nephrol. 2019;20:401. PMID 31672135. DOI 10.1186/s12882-019-1560-2.
- Delgado C, et al. A Unifying Approach for GFR Estimation: Recommendations of the NKF-ASN Task Force. Am J Kidney Dis. 2022;79(2):268–288.e1. PMID 34563581. DOI 10.1053/j.ajkd.2021.08.003.
FAQ
No. These adult eGFR equations are not validated for pregnancy, and this page does not provide a pregnancy-specific estimate.
Sources: [11]
No. CKD requires abnormalities of kidney structure or function—including reduced GFR or markers of kidney damage—to be present for at least 3 months. Acute illness, changing creatinine, and transient factors can make a single estimate unreliable.
Sources: [5]
No. They are displayed numerical ranges. G1 or G2 without another persistent kidney-damage marker does not establish CKD.
Sources: [5]
Results are mL/min/1.73 m². A nonindexed conversion multiplies indexed eGFR by BSA and divides by 1.73, but this page does not collect BSA or perform that conversion.
Sources: [9]
No. Referral depends on the full clinical context, cause, albuminuria, trend, complications, and applicable care pathways.
Sources: [5]
No. A numerical estimate alone cannot decide dialysis or transplant assessment.
Sources: [5]
Related Calculators
CrCl
Estimate adult Cockcroft–Gault creatinine clearance in mL/min from an explicit weight basis, without automatic weight selection or a dosing recommendation.
BSA
Calculate estimated body surface area from height and weight using the Mosteller, Du Bois, or Haycock formula.
UPCR / PCR
Calculate a same-specimen spot urine total protein-to-creatinine ratio in mg/mg, mg/g, and mg/mmol; not ACR, 24-hour protein, or a diagnosis.
Disclaimer
Educational and informational reference only. Not intended to replace professional medical advice, diagnosis, treatment, or independent verification.