Kidney filtration screening

GFR Calculator

This calculator estimates glomerular filtration rate (GFR), reported clinically as estimated GFR (eGFR), from serum creatinine in a blood test. Adults use the Chronic Kidney Disease Epidemiology Collaboration 2021 equation (CKD-EPI 2021), with optional Modification of Diet in Renal Disease (MDRD) comparison; patients under 18 use the Schwartz height-based equation. It assigns chronic kidney disease (CKD) stage and compares your result to an age-group average. Educational screening only; not a diagnosis or medical advice.

By Jeff Beem

Updated June 25, 2026

Estimated glomerular filtration rate (eGFR); educational only; runs locally.

Patient

Profile

Adult: CKD-EPI 2021 (Chronic Kidney Disease Epidemiology Collaboration) + MDRD (Modification of Diet in Renal Disease). Pediatric: Schwartz.

Age

Biological sex

Race (MDRD only)

CKD-EPI 2021 (Chronic Kidney Disease Epidemiology Collaboration) is race-neutral.

Serum creatinine (S_cr)

mg/dL

Typical adult ref.: ~0.6–1.2 mg/dL (53–106 μmol/L).

Calculations run in your browser. Nothing is stored or sent.

Results

Chronic kidney disease (CKD) stage

Stage 1

Normal or High

Population mean

93 mL/min/1.73m²

98.6% of mean

Normal kidney function

CKD-EPI 2021

Chronic Kidney Disease Epidemiology Collaboration; race-neutral

MDRD

Modification of Diet in Renal Disease; race-adjusted

General information

This estimate looks normal. Unexpected creatinine rises or protein in urine still warrant follow-up with a clinician.

Educational only, not medical advice. Discuss results with a clinician.

Chronic kidney disease stages

Chronic kidney disease (CKD) stages by estimated glomerular filtration rate (GFR) and typical follow-up framing
Stage	GFR (mL/min/1.73m²)	Description	Typical follow-up
1	≥90	Normal or high	Routine monitoring
2	60–89	Mildly decreased	Every 6–12 months; blood pressure / glucose
3a	45–59	Moderately decreased	Nephrology; every 3–6 months
3b	30–44	Moderate–severe	Active nephrology care
4	15–29	Severely decreased	Dialysis / transplant planning
5	<15	Kidney failure	Dialysis or transplant

How to use this calculator

Choose Adult or Pediatric in 01, then enter age, biological sex, and serum creatinine (mg/dL or μmol/L). With adult defaults (age 50, male, creatinine 1.0 mg/dL), CKD-EPI 2021 (Chronic Kidney Disease Epidemiology Collaboration) returns about 92 mL/min/1.73m² as the primary estimated glomerular filtration rate (eGFR), with MDRD (Modification of Diet in Renal Disease) near 79 for comparison; set race only for MDRD. Pediatric mode requires height (cm or ft/in) for the Schwartz equation (example: age 10, height 120 cm, creatinine 1.0 → eGFR ≈ 50). Results in 02 show eGFR, chronic kidney disease (CKD) stage, age-group mean, formula comparison, and general educational guidance only.

Reading estimated GFR in context

Serum creatinine alone is a poor storyteller. Estimated glomerular filtration rate (eGFR) formulas bake in age and sex (and height in children) because muscle mass drives creatinine production. Section 02 shows chronic kidney disease (CKD) stage, an age-group mean, formula comparison for adults, and general guidance text.

Example: age 50, male, creatinine 1.0 mg/dL

With Adult selected and defaults (age 50, male, creatinine 1.0 mg/dL, race set to not Black for MDRD only): CKD-EPI 2021 ≈ 92 mL/min/1.73m², which maps to Stage 1 (≥90) in the results card. The age-band mean for 50–59 is 93, so the widget shows about 98.6% of mean. MDRD in the comparison grid reads ≈ 79, which would be Stage 2 if it were primary; staging on this page always follows CKD-EPI for adults.

Example: pediatric (age 10, height 120 cm, creatinine 1.0 mg/dL, male)

On Pediatric with those inputs, Schwartz uses k = 0.413 and height 120 cm to estimate eGFR ≈ 50 mL/min/1.73m². The stage badge shows Stage 3a (45–59). Height drives the estimate in children; verify age is under 18 and height is measured standing.

Stages 3a and 3b in the results panel

When primary eGFR falls between 45 and 59, the widget labels Stage 3a (“Moderately Decreased”). Between 30 and 44, it shows Stage 3b. The chronic kidney disease stage table on this page lists typical follow-up framing (for example, nephrology every 3–6 months for 3a). The yellow “General information” box may suggest nephrology referral when eGFR is below 60; eGFR alone does not trigger dialysis planning.

Reading the CKD-EPI vs MDRD tiles in section 02

When Adult is selected, section 02 shows two numbered tiles: CKD-EPI 2021 (primary, race-neutral) and MDRD (uses the race toggle in section 01). At defaults (age 50, male, creatinine 1.0 mg/dL, race not Black), CKD-EPI reads ≈ 92 and MDRD ≈ 79. If the two tiles diverge by more than a few points, or either sits far below the age-band mean in the stage card, repeat the blood test and discuss context with a clinician.

What the guidance box does not do

The amber “General information” panel summarizes educational next steps by stage (repeat labs, nephrology referral, urgent care language for stage 5). It does not adjust medication doses, order imaging contrast, or replace clinical judgment. Bring your eGFR printout to prescribing visits; metformin and IV contrast decisions require a clinician.

GFR calculator: CKD-EPI, MDRD, and Schwartz eGFR

This calculator estimates glomerular filtration rate (eGFR) from serum creatinine in a blood test, assigns chronic kidney disease (CKD) stage, and compares your result to an age-group average. Educational screening only; not medical advice or a diagnosis.

What this calculator does

The widget computes estimated glomerular filtration rate (eGFR) in mL/min/1.73m² from serum creatinine. Adults receive CKD-EPI 2021 as the primary estimate and MDRD for side-by-side comparison; patients under 18 use Schwartz with height. Outputs include Kidney Disease: Improving Global Outcomes (KDIGO)–style chronic kidney disease (CKD) stage, an age-band population mean, a kidney function meter, formula comparison for adults, educational guidance text, and a stage table with typical follow-up framing. It does not measure cystatin C, urine albumin, or true inulin clearance, and it does not store or transmit your entries.

CKD-EPI 2021 (adult, primary):

$\text{eGFR} = 142 \times (S_{\text{cr}}/k)^a \times 0.9938^{\text{Age}} \times \text{sex factor}$
k = 0.7 (female) or 0.9 (male); exponent a depends on creatinine relative to k; female sex factor 1.012 when applicable.
MDRD (adult, comparison):

$\text{eGFR} = 175 \times S_{\text{cr}}^{-1.154} \times \text{Age}^{-0.203} \times (0.742 \text{ if female}) \times (1.212 \text{ if Black})$
Race adjustment applies only to MDRD in this widget; CKD-EPI 2021 does not use race.
Schwartz (pediatric):

$\text{eGFR} = k \times \frac{\text{Height (cm)}}{S_{\text{cr}}}$
k: 0.33 (<1 yr), 0.413 (1–12 yr), 0.7 (male adolescent), 0.55 (female adolescent).

How the math works

Start with the default adult profile: age 50, biological sex male, serum creatinine 1.0 mg/dL, and race set to not Black (MDRD only). CKD-EPI 2021 compares creatinine to k = 0.9 for males. Because 1.0 is above 0.9, the exponent is −1.2. The widget multiplies 142 by (creatinine ÷ k) raised to that power, then by 0.9938 raised to the age (50), which yields a primary eGFR of about 92 mL/min/1.73m².

That value maps to Stage 1 (≥90) in the results card. The age-band mean for someone aged 50–59 is 93, so the widget also shows you are at about 98.6% of the population mean for your decade. MDRD uses a separate creatinine exponent and age term; with the same inputs it returns about 79, which would be Stage 2 if it were primary. Staging on this page always follows CKD-EPI for adults.

In pediatric mode, height replaces age-and-sex muscle proxies. For age 10, height 120 cm, creatinine 1.0 mg/dL, and male sex, Schwartz selects k = 0.413 and computes 0.413 × 120 ÷ 1.0 ≈ 50 mL/min/1.73m², labeled Stage 3a (45–59). Creatinine entered as μmol/L is converted to mg/dL (÷ 88.4) before any formula runs.

Limits of the model

Creatinine-based eGFR is a screening estimate, not a diagnosis. Chronic kidney disease requires persistence for at least three months plus, in many cases, urine albumin or structural damage markers that this widget does not accept. Muscle mass, diet, supplements, and acute illness can move creatinine without a matching change in true filtration. Cystatin C–based equations and measured clearance are more accurate in some populations but are out of scope here. Always interpret results with a clinician; do not start, stop, or change medications based on this page alone.

FAQ

What is a normal eGFR for my age?

Estimated glomerular filtration rate (eGFR) naturally declines with age (roughly 1 mL/min/1.73m² per year after 40). This widget compares your primary result to an age-band mean shown in the results card: about 116 (20–29), 107 (30–39), 99 (40–49), 93 (50–59), 85 (60–69), 75 (70–79), and 65 (80+). A number near the mean is not automatically healthy if creatinine or urine protein is abnormal.

Which formula does this calculator use first?

For adults (18+), Chronic Kidney Disease Epidemiology Collaboration 2021 (CKD-EPI 2021), which is race-neutral, is the primary estimate shown in the dark results card. Modification of Diet in Renal Disease (MDRD), with an optional race factor you set in section 01, appears side-by-side for comparison. Patients under 18 use the Schwartz equation with height in centimeters or feet and inches. True glomerular filtration rate (GFR) from clearance studies is not modeled.

When is eGFR below 60 considered CKD?

Kidney Disease: Improving Global Outcomes (KDIGO) defines chronic kidney disease (CKD) as eGFR <60 mL/min/1.73m² for ≥3 months, with or without kidney damage markers such as albumin in urine. A single calculator result is not a diagnosis. The stage badge in section 02 is educational framing only.

Why can CKD-EPI and MDRD disagree?

The two adult formulas use different creatinine exponents and age terms. MDRD was tuned on chronic kidney disease cohorts and often reads lower when eGFR is still relatively high. At defaults (age 50, male, creatinine 1.0 mg/dL), CKD-EPI 2021 ≈ 92 while MDRD ≈ 79. Compare both in the formula comparison grid; large gaps or values far below your age-band mean warrant discussion with a clinician.

Can eGFR be wrong in muscular or frail patients?

Yes. Serum creatinine reflects muscle mass, not kidney function directly. The widget adjusts for age and biological sex in adult formulas and for height in pediatric Schwartz, but bodybuilders, amputees, cachexia, pregnancy, and acute illness can still skew estimates. Repeat labs, urine albumin, and clinical context matter when the number surprises you.

How does pediatric Schwartz work here?

Switch to Pediatric in section 01, enter age under 18, height, and serum creatinine. The widget picks a k constant by age band: 0.33 (under 1 year), 0.413 (1–12 years), 0.7 (male adolescents 13+), or 0.55 (female adolescents 13+), then computes eGFR = k × height (cm) ÷ creatinine (mg/dL). Example: age 10, height 120 cm, creatinine 1.0 mg/dL → eGFR ≈ 50 mL/min/1.73m².

Can I enter creatinine in μmol/L?

Yes. Toggle serum creatinine units in section 01. The widget converts μmol/L to mg/dL internally (divide by 88.4) before running CKD-EPI, MDRD, or Schwartz. Default adult creatinine is 1.0 mg/dL, which equals 88.4 μmol/L.

How often should GFR be rechecked?

Follow-up depends on stage, trend, and conditions like diabetes or hypertension. The chronic kidney disease stage table on this page lists typical monitoring intervals by stage (for example, every 3–6 months for stage 3a). Your clinician sets the actual schedule; this widget does not send reminders or store results.

Sources & citations

References used for the calculation method and definitions. Links open in a new tab when available.

[1]

Inker LA et al. New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race (CKD-EPI 2021). N Engl J Med. 2021;385(19):1737-1749

CKD-EPI 2021 race-neutral eGFR equation.

[2]

KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD

Kidney Disease: Improving Global Outcomes (KDIGO) CKD staging and eGFR-based clinical frameworks.

Fitness Reference Note

Informational Use: These calculations (BMI, Calories, etc.) are based on standard statistical formulas and are intended for general reference and goal-setting purposes only.

Consult Experts: This tool does not provide medical advice, diagnosis, or treatment. Results may not be accurate for athletes, pregnant individuals, or those with underlying health conditions.

Health Safety: Always consult with a healthcare professional or qualified trainer before beginning any new diet or intensive exercise program.

Privacy First: All calculations are performed locally in your browser. No health data is stored or transmitted to any server.