Calculate Estimated Glomerular Filtration Rate using the CKD-EPI 2021 Formula
Standard reference range is approx 0.6 to 1.2 mg/dL
Estimated GFR
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Units: mL/min/1.73m²
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Understanding the eGFR Calculation Formula
The Estimated Glomerular Filtration Rate (eGFR) is widely considered the best overall index of kidney function. It estimates how much blood passes through the glomeruli (the tiny filters in the kidneys) each minute. This calculator utilizes the CKD-EPI 2021 Creatinine Equation, which is recommended by the National Kidney Foundation and the American Society of Nephrology because it does not include race as a variable, ensuring equitable clinical assessment.
The Calculation Logic
The CKD-EPI 2021 formula calculates eGFR based on serum creatinine, age, and gender. The mathematics differ slightly for males and females due to differences in muscle mass, which affects creatinine generation.
The variables are:
Scr: Serum Creatinine in mg/dL
Age: In years
κ (Kappa): 0.7 for females, 0.9 for males
α (Alpha): -0.241 for females, -0.302 for males
Chronic Kidney Disease (CKD) Stages
Your eGFR result places kidney function into one of several stages, ranging from normal function to kidney failure.
Stage
eGFR Range
Description
G1
90 or higher
Normal or high kidney function (if other signs of kidney damage are present).
G2
60 – 89
Mildly decreased kidney function.
G3a
45 – 59
Mildly to moderately decreased kidney function.
G3b
30 – 44
Moderately to severely decreased kidney function.
G4
15 – 29
Severely decreased kidney function.
G5
Less than 15
Kidney failure (End Stage Renal Disease).
Why is eGFR Important?
Early stages of kidney disease often have no symptoms. By checking serum creatinine levels and calculating eGFR, doctors can detect kidney disease early. Regular monitoring allows for interventions that can slow the progression of kidney damage, manage complications, and prevent kidney failure.
Clinical Note
While this calculator provides a useful estimate, eGFR is an estimation. Factors such as extreme muscle mass (bodybuilders or amputees), diet (vegetarian vs high meat), and specific medications can influence creatinine levels independently of kidney function. Always consult a healthcare professional for a comprehensive diagnosis.
function calculateEGFR() {
// Get input elements
var ageInput = document.getElementById("age");
var creatinineInput = document.getElementById("creatinine");
var genderMale = document.getElementById("genderMale");
var resultContainer = document.getElementById("result-container");
var egfrDisplay = document.getElementById("egfrResult");
var stageDisplay = document.getElementById("stageResult");
var stageDesc = document.getElementById("stageDescription");
// Parse values
var age = parseFloat(ageInput.value);
var scr = parseFloat(creatinineInput.value);
var isMale = genderMale.checked;
// Validation
if (isNaN(age) || isNaN(scr) || age <= 0 || scr = 90) {
stageText = "Stage G1";
stageClass = "stage-g1";
description = "Normal or high kidney function.";
} else if (egfr >= 60) {
stageText = "Stage G2";
stageClass = "stage-g2";
description = "Mildly decreased kidney function.";
} else if (egfr >= 45) {
stageText = "Stage G3a";
stageClass = "stage-g3a";
description = "Mildly to moderately decreased kidney function.";
} else if (egfr >= 30) {
stageText = "Stage G3b";
stageClass = "stage-g3b";
description = "Moderately to severely decreased kidney function.";
} else if (egfr >= 15) {
stageText = "Stage G4";
stageClass = "stage-g4";
description = "Severely decreased kidney function.";
} else {
stageText = "Stage G5";
stageClass = "stage-g5";
description = "Kidney failure.";
}
// Update DOM
egfrDisplay.innerHTML = finalEgfr;
stageDisplay.innerHTML = stageText;
stageDisplay.className = "result-stage " + stageClass;
stageDesc.innerHTML = description;
resultContainer.style.display = "block";
}