Estimated Glomerular Filtration Rate (eGFR) is a blood test used to check how well your kidneys are working. Since the kidneys filter waste products from the blood, a lower eGFR suggests that kidney function may be impaired.
The standard formula used today is the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation. As of 2021, the updated formula removes race as a variable to ensure more equitable care, focusing instead on serum creatinine, age, and sex.
The CKD-EPI (2021) Formula
The calculation follows this mathematical structure:
Note: This calculator is for educational purposes. Clinical decisions should always be made in consultation with a medical professional.
function calculateEGFR() {
var scr = parseFloat(document.getElementById('scr').value);
var age = parseFloat(document.getElementById('age').value);
var sex = document.getElementById('gender').value;
if (isNaN(scr) || isNaN(age) || scr <= 0 || age = 90) {
stage = "Stage 1 (Normal)";
color = "#27ae60";
desc = "Your eGFR is in the normal range. If you have other evidence of kidney damage (like protein in the urine), this is classified as Stage 1 CKD.";
} else if (finalResult >= 60) {
stage = "Stage 2 (Mild Decrease)";
color = "#f1c40f";
textColor = "#000";
desc = "A result between 60-89 indicates a mild decrease in kidney function.";
} else if (finalResult >= 45) {
stage = "Stage 3a (Mild-Moderate Decrease)";
color = "#e67e22";
desc = "This indicates a mild to moderate loss of kidney function. Consult a physician for monitoring.";
} else if (finalResult >= 30) {
stage = "Stage 3b (Moderate-Severe Decrease)";
color = "#d35400";
desc = "This indicates a moderate to severe loss of kidney function. Medical management is typically required.";
} else if (finalResult >= 15) {
stage = "Stage 4 (Severe Decrease)";
color = "#c0392b";
desc = "This indicates a severe loss of kidney function. You may be approaching kidney failure.";
} else {
stage = "Stage 5 (Kidney Failure)";
color = "#000000";
desc = "This is end-stage renal disease (ESRD). Urgent medical attention is required.";
}
var resBox = document.getElementById('resultBox');
var valEl = document.getElementById('egfrValue');
var stageEl = document.getElementById('egfrStage');
var descEl = document.getElementById('stageDesc');
valEl.innerHTML = finalResult;
stageEl.innerHTML = stage;
stageEl.style.backgroundColor = color;
stageEl.style.color = textColor;
descEl.innerHTML = desc;
resBox.style.display = 'block';
resBox.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}