Gfr Calculator

by
GFR Calculator (Glomerular Filtration Rate)
CKD-EPI (2021 Race-Free Equation)MDRD Study EquationCockcroft-Gault (Creatinine Clearance)
MaleFemale
Estimated GFR Result:

mL/min/1.73m²
function toggleInputs(){var method=document.getElementById('method').value;var weightRow=document.getElementById('weightRow');if(method==='cockcroft'){weightRow.style.display='table-row';}else{weightRow.style.display='none';}}function calculateResult(){var scr=parseFloat(document.getElementById('creatinine').value);var age=parseFloat(document.getElementById('age').value);var gender=document.getElementById('gender').value;var method=document.getElementById('method').value;var showSteps=document.getElementById('steps').checked;if(isNaN(scr)||isNaN(age)){alert('Please enter valid numbers for creatinine and age.');return;}var gfr=0;if(method==='ckdepi'){var kappa=(gender==='female'?0.7:0.9);var alpha=(gender==='female'?-0.241:-0.302);var multiplier=(gender==='female'?1.012:1.0);gfr=142*Math.pow(Math.min(scr/kappa,1),alpha)*Math.pow(Math.max(scr/kappa,1),-1.200)*Math.pow(0.9938,age)*multiplier;}else if(method==='mdrd'){var mdrdMult=(gender==='female'?0.742:1.0);gfr=175*Math.pow(scr,-1.154)*Math.pow(age,-0.203)*mdrdMult;}else if(method==='cockcroft'){var weight=parseFloat(document.getElementById('weight').value);if(isNaN(weight)){alert('Please enter weight for Cockcroft-Gault calculation.');return;}var ccMult=(gender==='female'?0.85:1.0);gfr=((140-age)*weight)/(72*scr)*ccMult;}document.getElementById('resultValue').innerHTML=gfr.toFixed(1);var stageText="";if(showSteps){if(gfr>=90)stageText="Stage 1: Normal or high function";else if(gfr>=60)stageText="Stage 2: Mildly decreased function";else if(gfr>=45)stageText="Stage 3a: Mildly to moderately decreased function";else if(gfr>=30)stageText="Stage 3b: Moderately to severely decreased function";else if(gfr>=15)stageText="Stage 4: Severely decreased function";else stageText="Stage 5: Kidney failure";}document.getElementById('stageInfo').innerHTML=stageText;}

Using the GFR Calculator

A gfr calculator is a critical tool used by medical professionals and patients to estimate how well the kidneys are filtering waste from the blood. GFR stands for Glomerular Filtration Rate. Because direct measurement of GFR is complicated and requires specialized clinical settings, mathematical formulas are used to provide an estimate (eGFR) based on a simple blood test called serum creatinine.

By entering your lab results and demographic data into this tool, you can determine your kidney function stage and monitor health over time.

Serum Creatinine
Creatinine is a waste product from muscle breakdown. When kidneys aren't working well, creatinine levels in the blood rise.
Age & Biological Sex
Kidney function naturally declines with age, and muscle mass (which affects creatinine) differs between sexes.
Calculation Method
Choose between the modern CKD-EPI 2021 formula, the older MDRD formula, or the Cockcroft-Gault clearance method.

How It Works: The Formulas

The gfr calculator primarily uses the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation. In 2021, a new version was released that removed race as a variable to increase equity in healthcare. The formula is as follows:

eGFR = 142 × min(Scr/κ, 1)α × max(Scr/κ, 1)-1.200 × 0.9938Age [× 1.012 if female]

  • Scr: Serum creatinine in mg/dL
  • κ (kappa): 0.7 for females, 0.9 for males
  • α (alpha): -0.241 for females, -0.302 for males
  • min/max: Mathematical functions to determine the lower or higher of two values

Calculation Example

Example: A 55-year-old male with a serum creatinine level of 1.4 mg/dL.

Step-by-step solution (CKD-EPI 2021):

  1. Gender: Male (κ = 0.9, α = -0.302)
  2. Scr/κ: 1.4 / 0.9 = 1.55
  3. min(1.55, 1) = 1.0
  4. max(1.55, 1) = 1.55
  5. Calculate: 142 × (1.0)-0.302 × (1.55)-1.200 × (0.9938)55
  6. Work: 142 × 1.0 × 0.589 × 0.710
  7. Result GFR = 59.4 mL/min/1.73m² (Stage 3a)

Stages of Chronic Kidney Disease (CKD)

Doctors use the gfr calculator result to categorize kidney disease into five distinct stages:

StageGFR RangeDescription
Stage 190 or higherNormal function, but some signs of kidney damage.
Stage 260 to 89Mildly decreased kidney function.
Stage 3a45 to 59Mild to moderate loss of kidney function.
Stage 3b30 to 44Moderate to severe loss of kidney function.
Stage 415 to 29Severe loss of kidney function.
Stage 5Less than 15Kidney failure; dialysis or transplant may be needed.

Common Questions

Why did my GFR change suddenly?

Dehydration, certain medications (like ibuprofen), or a high-protein meal before the test can temporarily lower your GFR. It is always best to look at trends over several months rather than a single reading.

Is the CKD-EPI formula more accurate than MDRD?

Yes, most medical bodies now recommend CKD-EPI because it is more accurate, especially for patients with GFR values above 60 mL/min, where the MDRD formula tends to underestimate function.

Can I increase my GFR?

While you cannot usually reverse permanent kidney damage, you can prevent further decline by managing blood pressure, controlling blood sugar (if diabetic), and eating a kidney-friendly diet as recommended by your physician.

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