How the same age and sex translate creatinine into estimated GFRLive current inputs
Health & Fitness
Kidney Function Estimate Calculator
Estimate adult eGFR with the race-free 2021 CKD-EPI creatinine equation, show the exact branch used, de-index for body size when requested, and retain the uncertainty of an estimated—not measured—GFR.
2021 CKD-EPI eGFR—
GFR category label—
Creatinine-to-kappa ratio—
Equation branch—
Estimated body surface area—
De-indexed GFR estimate—
Estimation uncertainty context—
Interpretation boundary—
Equation response curve
How the same age and sex translate creatinine into estimated GFR
The nonlinear curve holds age and sex constant, marks the entered creatinine, and shades the broad GFR categories without suggesting that a single point establishes chronic disease.
Creatinine sensitivity table
Nearby creatinine values and their eGFR estimates
Values around the entered laboratory result reveal the nonlinear response and discourage reading a small creatinine difference as a fixed eGFR change.
| Creatinine | eGFR | G category | Change from entered | Use |
|---|
Laboratory setup
Use the calculator only with an adult standardized creatinine result
- Confirm the result is serum creatinine in mg/dL; divide micromoles per liter by 88.4 if conversion is required.
- Use age at the time of the sample.
- Enter the equation sex constant required by the published equation.
- Use height and weight only when a de-indexed estimate is relevant.
- Interpret eGFR with urine albumin, prior results, clinical context, and the laboratory report.
Estimate, not measurement
Creatinine reflects filtration and non-GFR biology
Muscle mass, diet, medications, acute illness, assay variation, and rapidly changing kidney function can alter serum creatinine independently of stable GFR.
NIDDK notes that trends are often more informative than one result and that creatinine-cystatin C equations may be preferable near critical decisions. The page therefore keeps uncertainty and decision boundaries visible.
2021 CKD-EPI creatinine equation
Use the exact minimum and maximum power branches
The equation uses age, sex-specific kappa and alpha constants, and standardized serum creatinine. The normalized result is indexed to 1.73 square meters; de-indexing uses Mosteller body surface area.
Detailed calculation process and general formulas
r = SCr / kappaeGFR = 142 x min(r,1)^alpha x max(r,1)^-1.200 x 0.9938^Age x ff = 1.012 if female; otherwise 1BSA = sqrt(height_cm x weight_kg / 3600)GFR_abs = eGFR x BSA / 1.73Symbols, meanings, and units
- SCr
- standardized serum creatininemg/dL
- kappa
- sex-specific creatinine constantmg/dL
- alpha
- sex-specific exponentdimensionless
- BSA
- Mosteller body surface aream2
- eGFR
- indexed estimated glomerular filtration ratemL/min/1.73 m2
Result anatomy
Three numbers that must not be conflated
Indexed eGFR, absolute estimated clearance, and a CKD category answer different questions.
Indexed eGFR
—Used for standardized kidney-function comparison and G-category context.
De-indexed estimate
—Adjusts for entered body surface area and may be relevant to some drug-dosing discussions.
Category context
—A G category alone does not establish chronicity, cause, or treatment.
Decision takeaway: Use the laboratory's reported equation and clinical context for decisions; do not substitute an online estimate for care.
Context to gather
Information that can change interpretation
- Prior eGFR and creatinine results
- Urine albumin-to-creatinine ratio
- Recent illness or dehydration
- Muscle mass or amputation
- Creatinine-affecting medicines
- Cystatin C when clinically appropriate
Applied decisions
Why the same creatinine does not mean the same eGFR
Two adults of different ages
Serum creatinine is held constant while age changes.
What the result clarifies: The age term changes the estimate even though the laboratory concentration is identical.
Decision near a dosing cutoff
The estimate lies close to a medication-label threshold.
What the result clarifies: The result should prompt equation and units verification, not automatic dose selection.
Worked default scenario
Current-input substitution and reconciliation
Method references
Evidence used to frame this specific model
Scope and limitations
For adults only. This estimate cannot diagnose CKD, acute kidney injury, or kidney failure. Chronic kidney disease generally requires persistent abnormalities or other markers of kidney damage. Seek urgent care for severe illness, markedly reduced urine, swelling with breathlessness, confusion, or other acute concerns.
Kidney Function Estimate Calculator | 2021 CKD-EPI eGFR FAQ
Does eGFR below 60 always mean CKD?
No single result establishes chronicity. Persistence, urine albumin, other kidney-damage markers, and clinical context matter.
Why is race not an input?
The 2021 CKD-EPI creatinine equation is race-free.
Why show de-indexed GFR?
Some medication-clearance discussions use an absolute estimate, but the drug label and clinician determine the appropriate method.
Would cystatin C improve the estimate?
NIDDK notes that combined creatinine-cystatin C equations are often more accurate, especially near critical decisions.