Estimated GFR uses serum creatinine, age, and a sex parameter to estimate kidney filtration. This adult tool applies the 2021 CKD-EPI creatinine equation without a race variable. Your lab may use a different equation.
Equation and units
eGFR = 142 × min(Scr/κ, 1)α × max(Scr/κ, 1)−1.200 × 0.9938age × 1.012 for the female parameter. Scr is IDMS-standardized serum creatinine in mg/dL; κ is 0.7 (female) or 0.9 (male), and α is −0.241 (female) or −0.302 (male). The tool converts µmol/L to mg/dL by dividing by 88.4. Output is in mL/min/1.73 m².
Find the correct values on your laboratory report
Locate serum creatinine and its unit on the report. Do not enter urine creatinine or a laboratory's already-calculated eGFR as the creatinine input. Enter age in completed years and the appropriate equation parameter. Assay calibration and the laboratory's reporting method can affect comparisons. The tool's permitted creatinine range of 0.1–30 mg/dL is a software input check, not a validated clinical range for every situation.
| Serum creatinine on the report | Result in this calculator |
|---|---|
| 1.00 mg/dL | About 97.6 mL/min/1.73 m² · G1 |
| 88.4 µmol/L | About 97.6 mL/min/1.73 m² · G1 |
These are the same hypothetical input expressed in two units. A G1 category does not establish that urine albumin is normal or replace a clinical assessment.
Calculation checks and software corrections
Checked 1 November 2026: these hypothetical inputs match NKF implementation Table S1. The table is for the creatinine-only mode: leave cystatin C blank. We calculated the equation separately and compared it with the enhanced calculator code used on this page. eGFR is in mL/min/1.73 m².
| Age | Equation sex parameter | Creatinine (mg/dL) | This tool displays | NKF integer reference |
|---|---|---|---|---|
| 18 | Male | 0.90 | 127.0 | 127 |
| 18 | Male | 0.91 | 125.3 | 125 |
| 18 | Female | 0.70 | 128.5 | 128 |
| 18 | Female | 0.71 | 126.3 | 126 |
| 90 | Male | 0.50 | 96.9 | 97 |
| 90 | Male | 1.50 | 44.0 | 44 |
| 90 | Female | 0.50 | 89.0 | 89 |
| 90 | Female | 1.50 | 32.9 | 33 |
This tool displays one decimal place; the NKF table displays integers. Each is rounded from the original calculation, so do not round 128.5 again to compare it with the NKF integer. Local code checks covered both creatinine-only and creatinine–cystatin C modes, unit conversion, input boundaries and GFR categories. Desktop-browser checks of both language pages covered representative calculations, the exclusion checkbox and result previews; the eight table examples were also entered in the English interface.
Input-boundary correction: 8.84 µmol/L was rejected because of floating-point conversion error. The tool now checks the permitted range in the selected unit (0.1–30 mg/dL or 8.84–2,652 µmol/L) and rejects values immediately outside it. We also corrected category labels in the result and preview so they use the unrounded estimate. Equation coefficients, the formulas, and numerical result rounding are unchanged.
These are software calculation checks with hypothetical inputs, not validation of clinical accuracy in real patients or independent medical review. They do not establish that every other calculator has been checked.
The displayed result is rounded to one decimal place, but the GFR category uses the unrounded value. For example, a calculated value of 59.95 can display as 60.0 while remaining in G3a (below 60). These are GFR categories, not a diagnosis of CKD.
What does the GFR category mean?
G1 is 90 or above; G2, 60 to below 90; G3a, 45 to below 60; G3b, 30 to below 45; G4, 15 to below 30; and G5, below 15. This is a GFR category, not a diagnosis. G1 or G2 alone does not establish chronic kidney disease (CKD), and one lower result cannot establish chronicity.
A clinical CKD assessment considers at least three months of persistence, urine albumin-to-creatinine ratio (uACR), cause, and prior results. An eGFR of 60 or higher does not rule out other signs of kidney damage.
When can creatinine-based eGFR be misleading?
This CKD-EPI eGFR is not valid for assessing kidney function during pregnancy. It is also invalid when creatinine changes rapidly, such as in acute kidney injury, or during dialysis. Do not use the displayed GFR category for clinical decisions in these situations; a clinician should assess creatinine trends and the appropriate tests.
Frailty in older adults, amputation, neuromuscular disease, unusually high or low muscle mass or body size, severe obesity or malnutrition, cancer and critical illness, some diets or creatine supplements, and certain medicines can affect the accuracy of a creatinine-based estimate. Creatinine assays should be standardized. For decisions requiring greater accuracy, a clinician may consider an equation that includes cystatin C or measured GFR. Cystatin C has limitations of its own.
For people aged 18–25 with mild to moderate CKD, the CKiD U25 equation may be more appropriate for clinical decisions than adult CKD-EPI. This tool does not calculate U25.
The female and male parameters represent population averages; gender identity or sex assigned at birth alone does not always select the appropriate parameter. For transgender, nonbinary, or other gender-diverse people, especially when gender-affirming hormone therapy is involved, review both estimates, muscle mass, hormone status, and the need for further testing with a clinician rather than assuming one parameter.
Can I use this result to adjust medicine?
The output is indexed to a body surface area of 1.73 m². Product labelling can require a different kidney measure or unit. Do not treat this as creatinine clearance (CrCl), or start, stop, or change a medicine dose from this page.
Frequently asked questions
Why is my lab-reported eGFR different?
Your lab may use another equation or report a rounded result; assay calibration and unit choices also matter. Check which method is on the report with your clinical team.
Does a G3a result mean I have stage 3 CKD?
G3a names the calculated filtration category. CKD classification also requires the relevant duration and clinical context, including urine albumin and the cause of kidney findings.
For the historical estimate in another unit, see the Cockcroft–Gault CrCl calculator. These two measures are not interchangeable.
What to check alongside this result
- Compare the date, serum creatinine and eGFR with previous reports. Ask your clinical team promptly about a new or markedly changed result.
- Review urinary albumin separately with the urine ACR calculator; serum and urine creatinine are different specimens.
- Use the creatinine and eGFR report guide and the eGFR versus CrCl guide to prepare questions about differences between results.
Related tools and sources
Health calculators · Adult BMI calculator. Contact your clinical team promptly for a new or markedly changed low result or concerning symptoms.
NKF: 2021 CKD-EPI equation · NIDDK: Adult GFR equations · NIDDK: Adult and young-adult calculators · NKF: GFR categories · KDIGO 2024 guideline · UK Kidney Association: Pregnancy guideline · UK Kidney Association: Kidney function measurement. Sources and examples checked by Life Choice Note, 26 September 2026. No independent physician review has been performed. This is general information and does not replace a laboratory report or individual medical advice. Editorial standards · Disclaimer