GFR Calculator
Calculate glomerular filtration rate using MDRD and CKD-EPI formulas for both adults and children. Assess kidney function and determine chronic kidney disease (CKD) stages with comprehensive medical information.
📋 Quick Navigation
MDRD Formula
CKD-EPI Formula
CKD Stage
📊 CKD Disease Staging
| Stage | GFR (mL/min/1.73m²) | Status | Clinical Notes |
|---|---|---|---|
| Normal | ≥90 | Healthy kidney function | No proteinuria |
| CKD1 | ≥90 | Kidney damage present | With proteinuria evidence |
| CKD2 (Mild) | 60-89 | Mildly decreased function | Kidney damage likely |
| CKD3 (Moderate) | 30-59 | Moderately decreased function | May require specialist care |
| CKD4 (Severe) | 15-29 | Severely decreased function | Preparation for kidney failure |
| CKD5 (Failure) | <15 | Kidney failure | Dialysis or transplant needed |
🧠 Understanding Glomerular Filtration Rate
What is GFR?
Glomerular filtration rate describes the rate of flow of filtered fluids through the kidney and is used as a measure of kidney function. GFR is measured in milliliters per minute per 1.73 square meters of body surface area (mL/min/1.73m²). A higher GFR indicates better kidney function, while a declining GFR may indicate kidney disease progression.
Normal GFR Ranges
Age 20-29: ~116 mL/min/1.73m². Age 30-39: ~107 mL/min/1.73m². Age 40-49: ~99 mL/min/1.73m². Age 50-59: ~93 mL/min/1.73m². Age 60-69: ~85 mL/min/1.73m². Age 70+: ~75 mL/min/1.73m². GFR naturally decreases with age, but a significant drop from your baseline may indicate kidney disease.
Why GFR Matters
Kidney Function Assessment: GFR is the best overall measure of kidney function. Early Disease Detection: Declining GFR can indicate early chronic kidney disease requiring intervention. Medication Dosing: Many drugs are adjusted based on GFR to prevent toxicity. Treatment Planning: GFR helps determine if dialysis or transplant may be needed. Prognosis: GFR helps predict kidney disease progression.
🧮 GFR Calculation Formulas
IDMS-Traceable MDRD Formula (for adults)
Where:
Scr = Serum creatinine in mg/dL
Age = in years
Multipliers are applied for female gender (×0.742) and Black race (×1.212)
CKD-EPI 2021 Formula (most current for adults)
GFR = 142 × min(Scr/κ, 1)α × max(Scr/κ, 1)-1.200 × (0.9938)age × 1.012 (if female)
Where:
κ = 0.7 (females) or 0.9 (males)
α = -0.241 (females) or -0.302 (males)
Age = in years
Schwartz Formula (for children)
Where:
Height = in centimeters
Scr = Serum creatinine in mg/dL
Most accurate for children under 18
🏥 Chronic Kidney Disease (CKD) Staging
Understanding CKD Stages
Chronic kidney disease is classified into 5 stages based on GFR. Each stage represents a different level of kidney function decline. The sooner kidney disease is diagnosed and treated, the better the outcomes. Treatment aims to slow progression and prevent complications.
Stage-Specific Management
Normal/CKD1: Maintain healthy lifestyle, manage blood pressure, control diabetes. Annual GFR monitoring. CKD2: Lifestyle changes, manage risk factors, blood pressure control. Check GFR yearly. CKD3: Manage complications (anemia, bone disease), evaluate cardiovascular risk. Check GFR twice yearly. CKD4: Specialist referral, prepare for kidney failure, manage complications. Check GFR quarterly. CKD5: Dialysis or transplant planning essential, frequent specialist visits.
Important CKD Considerations
GFR Decline Rate: Normal aging causes GFR to decline ~1 mL/min/1.73m² per year after age 30. Faster decline suggests kidney disease. Serum Creatinine Limitations: Creatinine depends on muscle mass, diet, and medications. Two people with same creatinine may have different actual kidney function. CKD Diagnosis: Requires persistent GFR <60 mL/min/1.73m² for ≥3 months OR evidence of kidney damage (proteinuria, hematuria, imaging).