GFR Calculator
Clinical GFR calculator supporting the modern 2021 race-free CKD-EPI standard, legacy MDRD study formula, Mayo quadratic equation, and pediatric Bedside Schwartz formula for children.
GFR Calculator
Glomerular Filtration Rate using the validated CKD-EPI formula.
Clinical Interpretation:
Normal kidney function. (GFR >= 90 mL/min/1.73m²)
Glomerular Filtration Rate (GFR): CKD-EPI Equation, Creatinine & Renal Function
Estimated Glomerular Filtration Rate (eGFR) evaluates kidney filtration capacity and screens for Chronic Kidney Disease (CKD) stages using serum creatinine and validated demographic adjustments.
The CKD-EPI 2021 Clinical Standard
The 2021 CKD-EPI creatinine equation removes race-based coefficients to deliver an unbiased, standardized metric of renal filtration expressed in mL/min/1.73 m².
An eGFR consistently above 90 indicates normal function, while values below 60 persistent for three or more months indicate Chronic Kidney Disease requiring nephrology evaluation.
Step-by-Step Instructions
Enter Serum Creatinine Level
Input laboratory blood serum creatinine concentration in mg/dL or µmol/L.
Specify Biological Sex & Age
Input age in years and biological sex (assigned at birth for physiological muscle mass baselines).
Input Serum Cystatin C (Optional)
Optionally add serum Cystatin C (mg/L) for the combined 2021 CKD-EPI Creatinine-Cystatin C clinical gold standard.
Review eGFR & CKD Staging
Evaluate estimated Glomerular Filtration Rate ($ ext{mL/min/1.73m}^2$) and National Kidney Foundation KDIGO chronic kidney disease staging (G1 to G5).
Key Features & Capabilities
- Official 2021 CKD-EPI Creatinine Equation (race-free clinical standard recommended by NKF and ASN)
- 2021 CKD-EPI Creatinine-Cystatin C combined equation for high-precision diagnostic confirmation
- MDRD (Modification of Diet in Renal Disease) legacy clinical equation comparison
- KDIGO Chronic Kidney Disease (CKD) Stage classification: Stage 1 ($\ge 90$), Stage 2 (60–89), Stage 3a (45–59), Stage 3b (30–44), Stage 4 (15–29), Stage 5 Kidney Failure ($< 15$)
Frequently Asked Questions
What is Glomerular Filtration Rate (GFR) and what does it measure?
Glomerular Filtration Rate (GFR) is the primary clinical biomarker measuring the flow rate of filtered fluid through the kidney's glomerular capillaries. It evaluates how efficiently your kidneys remove metabolic waste products (urea, creatinine, toxins) from blood plasma, normalized to a standard body surface area of 1.73 m².
What is the new 2021 race-free CKD-EPI equation?
In 2021, the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN) established a standardized race-free CKD-EPI equation that eliminated the historical race modifier. It calculates eGFR strictly using age, biological sex, and serum creatinine: $\text{eGFR} = 142 \times \min(S_{\text{cr}}/\kappa, 1)^\alpha \times \max(S_{\text{cr}}/\kappa, 1)^{-1.200} \times 0.9938^{\text{Age}} \times [1.012\text{ if female}]$. (where $\kappa = 0.7$ female / $0.9$ male; $\alpha = -0.241$ female / $-0.302$ male).
What are the five clinical stages of Chronic Kidney Disease (CKD)?
According to KDIGO clinical practice guidelines: **Stage 1 (Normal/High)**: eGFR ≥ 90 mL/min/1.73m² (with kidney damage/proteinuria); **Stage 2 (Mild Reduction)**: eGFR 60–89; **Stage 3a (Mild-to-Moderate)**: eGFR 45–59; **Stage 3b (Moderate-to-Severe)**: eGFR 30–44; **Stage 4 (Severe Reduction)**: eGFR 15–29; **Stage 5 (Kidney Failure / ESRD)**: eGFR < 15 mL/min/1.73m².
Why can high muscle mass or creatine supplementation artificially lower eGFR?
Creatinine is a breakdown byproduct of muscle creatine phosphate. Highly muscular athletes, bodybuilders, or individuals consuming daily creatine monohydrate supplements produce significantly higher baseline serum creatinine, artificially suppressing creatinine-based eGFR without indicating actual kidney damage. Testing **Serum Cystatin C** provides an accurate kidney evaluation independent of muscle mass.
Related Utilities
Discover complementary online tools in the same workflow.
Tire Size Calculator & Comparison Tool
Calculate tire dimensions, sidewall height, overall diameter, circumference, revs per mile, and speedometer calibration difference.
Roofing Calculator - Squares, Shingle Bundles & Cost
Calculate roofing squares, shingle bundles, underlayment felt rolls, roof pitch slope factor, and total material & labor cost.
Tile Calculator - Floor & Wall Tile Box Estimator
Calculate tile quantities, full box counts, grout line spacing, waste allowance, and material cost for floors, bathrooms, and backsplashes.
Mulch Calculator - Cubic Yards & Bag Estimator
Calculate cubic yards, cubic meters, bag counts (2 cu ft & 3 cu ft), and cost for landscaping garden beds and tree rings.
Gravel Calculator - Tons, Cubic Yards & Driveways
Calculate gravel tonnage, cubic yards, aggregate density presets (Crushed stone, Pea gravel, River rock, Road base), and project cost.
Wind Chill Calculator - NWS Index & Frostbite Time
Calculate the official National Weather Service (NWS) wind chill temperature index, feels-like cold, and frostbite danger exposure time.