Renal Function
Renal function calculators for eGFR, creatinine clearance (CrCl), and kidney-related estimates — with formulas and worked examples.
Creatinine Clearance (CrCl)
Calculate creatinine clearance using Cockcroft-Gault formula for medication dosing
eGFR Calculator
Estimate glomerular filtration rate using CKD-EPI formula for kidney function assessment
How Renal Function Calculations Work
Renal function calculators estimate kidney filtration and clearance using laboratory values (e.g., serum creatinine) and patient factors (age, sex, weight). These estimates help clinicians assess kidney function and support medication dosing discussions.
Common inputs include age, sex, weight (for CrCl), serum creatinine, and sometimes race. Different formulas are used for different purposes, and local protocols apply. Understanding the inputs and units is critical for accurate results.
Common Renal Function Calculations Explained
eGFR (estimated glomerular filtration rate)
eGFR is commonly reported with pathology results and is used as a general estimate of kidney filtration. Many labs calculate it automatically, but understanding inputs helps with checking.
Example question: A report lists eGFR and you want to understand what it represents. What inputs are typically used to calculate eGFR?
• Serum creatinine
• Age
• Sex
(± sometimes ethnicity in older equations)
Worked example
Result: eGFR is calculated from creatinine + demographics using a validated equation.
Tip: Always check creatinine units before comparing results.
Creatinine clearance (CrCl) — Cockcroft–Gault
CrCl estimates creatinine clearance using age, weight, sex, and serum creatinine. It's often used when a clearance estimate is required rather than lab-reported eGFR.
Example question: A patient is 60 years old, weighs 80 kg, and has serum creatinine 100 µmol/L. Estimate CrCl using Cockcroft–Gault (male example).
(Use unit conversion if creatinine is in µmol/L)
Worked example
Result: CrCl is calculated from age + weight + creatinine (with correct units).
Tip: CrCl is very unit-sensitive—convert creatinine correctly first.
BUN:Creatinine ratio
This ratio compares urea (BUN) to creatinine. It's a quick relationship check, but interpretation depends on clinical context.
Example question: BUN is 18 mg/dL and creatinine is 1.2 mg/dL. What is the BUN:Cr ratio?
Worked example
Result: BUN:Cr ratio = 15
Tip: Use matching units for the ratio.
When These Calculators Are Used
- •Understanding kidney filtration/clearance estimates from labs
- •Estimating CrCl when a clearance calculation is required
- •Checking unit conversions for creatinine (µmol/L vs mg/dL)
- •Supporting safe medication planning discussions (no dosing outputs)
- •Education/study for renal physiology and lab interpretation basics
Clinical Safety Note
Renal function estimates depend on the formula used and the units entered. Always confirm creatinine units and follow local protocols. These calculators support calculation checking but do not replace professional judgement. Examples on this page are for calculation practice only.
Related Calculator Categories
Frequently Asked Questions
Always confirm units and the required formula per local protocol.