Audited —·Last updated 27 Jul 2026·5 citations·Tier 1·0 uses

eGFR Calculator

Estimate CKD-EPI 2021 eGFR from age, sex, and serum creatinine with unit conversion and clinical limits.

eGFR Calculator

Sex (as used by CKD-EPI 2021)
Serum creatinine unit
CKD-EPI 2021 eGFR (mL/min/1.73 m2)
55.7635
Serum creatinine converted to mg/dL
1.1
Creatinine ratio (creatinine / kappa)
1.5714

Background.

An eGFR calculator estimates adult glomerular filtration rate from age, sex, and serum creatinine using the CKD-EPI 2021 creatinine equation. The canonical use case is a lab result or clinical note where a patient has a serum creatinine value but wants to understand the indexed estimated GFR number. For a 65-year-old female with serum creatinine of 1.1 mg/dL, the CKD-EPI 2021 creatinine equation gives 55.7634698084142 mL/min/1.73 m2. A product display may round that to 55.8, but the calculation should preserve full precision internally.

People search for eGFR because serum creatinine alone is difficult to interpret. Creatinine is affected by kidney filtration, but also by age, sex, muscle mass, diet, medications, assay differences, and acute illness. A creatinine of 1.1 mg/dL may be normal for one adult and abnormal for another. The CKD-EPI equation uses demographic and creatinine terms to convert the lab value into an indexed filtration estimate. NIDDK lists the 2021 equation for adult use and explains that estimating equations are used because measured GFR is more complex and resource intensive.

The 2021 equation matters because older eGFR equations included a race coefficient. Inker and colleagues published new race-free creatinine and creatinine-cystatin C equations in 2021. NIDDK now provides race-free adult equations and calculators. This dossier focuses on the creatinine-only equation because serum creatinine is the common input in routine metabolic panels. Cystatin C can improve assessment in selected patients, but it requires an additional lab value and a separate formula. The base calculator should not pretend to compute a cystatin C equation without that input.

The output must be labeled carefully. CKD-EPI eGFR is indexed to 1.73 m2 body surface area and is reported as mL/min/1.73 m2. Cockcroft-Gault creatinine clearance is a different calculation and has already been covered by a separate Quanta dossier. Drug labels may specify creatinine clearance or eGFR, so the calculator should not blur those terms. If engineering later adds a de-indexed eGFR mode, it should multiply the indexed eGFR by actual body surface area divided by 1.73 and label the result separately.

Clinical interpretation is also limited. KDIGO emphasizes chronic kidney disease evaluation through GFR, albuminuria, cause, and duration. A single eGFR value can be transiently low during dehydration, acute kidney injury, medication changes, or lab variation. CKD staging generally requires persistence and context. The calculator can show the arithmetic and an optional general note that lower eGFR values may warrant clinical review, but it should not diagnose chronic kidney disease or recommend treatment from one number.

For Quanta, this is a high-intent clinical calculator with strong SEO value and a clear relationship to existing renal calculators. It should support mg/dL and micromol/L creatinine entry, validate adult ages, prevent zero or negative creatinine, show the exact equation, and return a plain-language limitations note. It should also link to creatinine clearance, corrected calcium, anion gap, and body surface area so users can distinguish renal-function arithmetic from adjacent lab and dosing calculators.

What is egfr calculator?

An eGFR calculator is an adult kidney-function estimation tool. It uses an estimating equation to convert serum creatinine, age, and sex into an indexed estimate of glomerular filtration rate. The result is expressed in mL/min/1.73 m2, meaning it is normalized to a standard body surface area. The base formula in this dossier is the 2021 CKD-EPI creatinine equation.

The key terms are serum creatinine, estimated glomerular filtration rate, CKD-EPI, indexed GFR, kappa, alpha, sex factor, race-free equation, body surface area, albuminuria, and chronic kidney disease. Serum creatinine is a blood test related to creatinine generation and kidney excretion. CKD-EPI is the equation-development group. Kappa and alpha are sex-specific constants in the formula. Indexed GFR allows comparison across people of different body sizes but may not equal absolute filtration in mL/min.

The calculator is valid for adults when serum creatinine is available and the user wants the CKD-EPI 2021 creatinine estimate. It is not valid for children, pregnancy-specific interpretation, rapidly changing kidney function, unusual muscle mass without caution, cystatin C estimation without cystatin C, measured GFR, or drug dosing when the label requires Cockcroft-Gault creatinine clearance. It should be treated as a transparent calculation, not a diagnosis.

How to use this calculator.

  1. Enter age in completed years.
  2. Select sex as required by the CKD-EPI 2021 creatinine equation.
  3. Enter serum creatinine.
  4. Choose mg/dL or micromol/L as the creatinine unit.
  5. Review the converted creatinine and CKD-EPI 2021 eGFR result.
  6. Compare the result with the lab report and clinical context, including urine albumin results if available.
  7. Use clinician guidance for interpretation, follow-up testing, diagnosis, and medication decisions.

The formula.

eGFR = 142 × min(Scr⁄κ,1)^α × max(Scr⁄κ,1)^−1.200 × 0.9938^age
Scr · serum creatinine mg⁄dLκ · 0.7 female, 0.9 maleα · −0.241 female, −0.302 male0.9938^age · age term, age in years× 1.012 · female factor

The CKD-EPI 2021 creatinine equation is built from several multiplicative terms. The calculator first converts serum creatinine to mg/dL if needed. A micromol/L value is divided by 88.4. It then selects sex-specific constants. For females, kappa is 0.7, alpha is -0.241, and the sex factor is 1.012. For males, kappa is 0.9, alpha is -0.302, and the sex factor is 1. These constants are part of the published equation and should not be exposed as editable user assumptions.

The creatinine ratio is serum creatinine divided by kappa. The equation uses both the minimum of that ratio and 1, and the maximum of that ratio and 1. This split lets the equation curve change on either side of the sex-specific creatinine threshold. The minimum term is raised to alpha. The maximum term is raised to -1.200. Age is handled by multiplying by 0.9938 raised to the age in years. The final coefficient is 142, and the sex factor is applied at the end.

In the worked example, serum creatinine is already in mg/dL. Because the user selected female, kappa is 0.7 and alpha is -0.241. The creatinine ratio is 1.57142857142857. The minimum term is 1 because the ratio is above 1. The maximum term is 1.57142857142857 raised to -1.200, or 0.581361711632218. The age term is 0.9938 raised to 65, or 0.667474235533342. Multiplying 142 by 1, by 0.581361711632218, by 0.667474235533342, and by 1.012 gives 55.7634698084142.

The result is indexed, so its unit is mL/min/1.73 m2. That unit matters. A very small or very large adult can have an indexed eGFR that differs from absolute filtration used in some pharmacokinetic contexts. This base calculator should not silently de-index. If body surface area is provided in a future mode, the formula would be absoluteEgfrMlMin = indexedEgfr * bodySurfaceAreaM2 / 1.73, with the absolute value clearly labeled.

A worked example.

Example

The example user is a 65-year-old female with serum creatinine of 1.1 mg/dL. The calculator chooses the female constants from the CKD-EPI 2021 creatinine equation: kappa 0.7, alpha -0.241, and sex factor 1.012. Serum creatinine divided by kappa is 1.57142857142857. Because that ratio is greater than 1, the minimum term becomes 1 and the maximum term remains 1.57142857142857. The minimum term raised to alpha is 1. The maximum term raised to -1.200 is 0.581361711632218. The age term, 0.9938 raised to 65, is 0.667474235533342. Multiplying the equation coefficient and all terms gives 142 * 1 * 0.581361711632218 * 0.667474235533342 * 1.012, or 55.7634698084142 mL/min/1.73 m2. The calculator may show 55.8 for readability, but tests should compare against the full-precision value.

age Years65
serum Creatinine1.1

Frequently asked questions.

Is eGFR the same as creatinine clearance?
No. eGFR from the CKD-EPI equation is an indexed estimate of glomerular filtration rate, usually reported in mL/min/1.73 m2. Cockcroft-Gault creatinine clearance estimates creatinine clearance in mL/min and uses age, sex, weight, and serum creatinine. Drug labels and clinical protocols may specify one or the other. The calculator should label the equation so users do not substitute eGFR for creatinine clearance when a medication instruction requires Cockcroft-Gault.
Why does the calculator use the 2021 CKD-EPI equation?
The 2021 CKD-EPI creatinine equation is a race-free adult equation listed by NIDDK and published by Inker and colleagues. It replaced older equation workflows that included a race coefficient. The calculator uses it because it is current, widely cited, and suitable for a simple creatinine-based eGFR tool. The product should still show the exact equation and citations because some labs, institutions, and historical records may use different eGFR equations.
Can I use this calculator for children?
No. This dossier covers the adult CKD-EPI 2021 creatinine equation. Pediatric kidney-function estimation commonly uses different equations and inputs, such as height in the bedside Schwartz equation. A child or adolescent result should use pediatric guidance and the lab or clinician's preferred equation. The calculator should validate age and display an adult-use limitation rather than returning a misleading adult eGFR for a pediatric user.
Does one low eGFR mean chronic kidney disease?
Not by itself. Chronic kidney disease classification depends on kidney function, markers of kidney damage such as albuminuria, cause, and persistence over time. A single eGFR can be affected by acute illness, dehydration, medication changes, lab variation, or recent changes in kidney function. The calculator should compute the number and explain that diagnosis and staging require clinical context and repeat or supporting measurements when appropriate.
Why does serum creatinine sometimes mislead?
Creatinine is influenced by kidney filtration, but it is also influenced by muscle mass, diet, creatinine generation, assay methods, and medications. Older adults, amputees, bodybuilders, people with low muscle mass, pregnancy, and severe acute illness can all make creatinine-based estimates less reliable. NIDDK discusses factors that affect eGFR accuracy. The calculator should not hide this limitation, and users with unusual clinical circumstances may need cystatin C, measured GFR, or clinician interpretation.
What unit should I enter for creatinine?
Enter the unit shown on the lab report. Many United States reports use mg/dL, while many other settings use micromol/L. The calculator should let the user choose either. If micromol/L is selected, the value is divided by 88.4 to convert to mg/dL before the CKD-EPI equation is applied. Unit mistakes produce large errors, so the unit selector should be visible and stored with the result.
What does mL/min/1.73 m2 mean?
It means the estimate is indexed to a standard body surface area of 1.73 square meters. Indexing allows comparison across adults of different body sizes and is common in CKD staging and lab reporting. It is not the same as absolute filtration in mL/min. Some medication or pharmacokinetic decisions may need absolute kidney function or a specific drug-label method. The calculator should preserve the indexed unit unless it adds an explicit de-indexing mode.
Should the calculator show CKD stages?
It can show general GFR category labels only if the wording is careful and tied to persistence and clinical context. A single eGFR value should not be presented as a diagnosis. KDIGO classification uses GFR categories, albuminuria categories, cause, and duration. A basic calculator can provide the arithmetic and a neutral note, while a future clinical interpretation module could add configurable categories with stronger disclaimers and links to official guidance.

References& sources.

  1. [1]National Institute of Diabetes and Digestive and Kidney Diseases (2024). eGFR Equations for Adults. NIDDK.
  2. [2]National Institute of Diabetes and Digestive and Kidney Diseases. Estimated Glomerular Filtration Rate (eGFR) Calculators. NIDDK.
  3. [3]Inker, L.A. et al. (2021). New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race. New England Journal of Medicine.
  4. [4]Kidney Disease: Improving Global Outcomes (2024). KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. KDIGO.
  5. [5]National Institute of Diabetes and Digestive and Kidney Diseases. Factors Affecting eGFR Accuracy: Demographics. NIDDK.
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