eGFR Calculator
Calculate estimated glomerular filtration rate (eGFR) to assess kidney function. Uses CKD-EPI 2021 and MDRD equations with creatinine levels.
eGFR (CKD-EPI 2021)
92 mL/min/1.73m²
CKD Stage: G1
Normal or high
eGFR (MDRD)
79 mL/min/1.73m²
Creatinine
1.00 mg/dL (88.4 µmol/L)
CKD Stages Reference
| Stage | GFR | Description |
|---|---|---|
| G1 | ≥90 | Normal or high |
| G2 | 60-89 | Mildly decreased |
| G3a | 45-59 | Mild-moderate decrease |
| G3b | 30-44 | Moderate-severe decrease |
| G4 | 15-29 | Severely decreased |
| G5 | <15 | Kidney failure |
Clinical Notes
- • CKD-EPI 2021 is the current recommended equation
- • This calculator uses the race-free formulation
- • eGFR may be inaccurate in extremes of body size or muscle mass
- • Not validated for acute kidney injury (AKI)
- • Consider cystatin C-based equations for confirmation
Disclaimer: This calculator is for educational purposes only. Always consult a healthcare provider for medical decisions. eGFR is an estimate and may not reflect actual kidney function in all patients.
Related Calculators
About This Calculator
The estimated glomerular filtration rate (eGFR) is a key measure of kidney function used to detect and monitor chronic kidney disease (CKD). This calculator uses the latest CKD-EPI 2021 equation, which is race-free and recommended by major nephrology organizations worldwide.
What is GFR? Glomerular filtration rate (GFR) measures how well your kidneys filter waste from your blood. It's the volume of fluid filtered by the kidneys per minute, expressed as mL/min/1.73m² (normalized to body surface area). Higher GFR means better kidney function.
Why is eGFR Important?
- Detects kidney disease early, often before symptoms appear
- Stages chronic kidney disease (CKD)
- Guides medication dosing (many drugs are cleared by kidneys)
- Monitors disease progression
- Helps determine need for dialysis or transplant
The CKD-EPI 2021 Equation: This calculator uses the updated CKD-EPI equation that does not include race as a variable, following recommendations from the National Kidney Foundation and American Society of Nephrology.
For related kidney calculations, see our BSA Calculator. For overall health assessment, see our BMI Calculator.
How to Use the eGFR Calculator
- 1Enter the serum creatinine value from your blood test.
- 2Select the correct unit (mg/dL or µmol/L).
- 3Enter the patient's age in years.
- 4Select biological sex (male or female).
- 5View the calculated eGFR and CKD stage.
- 6Compare CKD-EPI 2021 with MDRD results.
- 7Review the CKD staging table for interpretation.
- 8Note the clinical considerations below.
- 9Consult a healthcare provider for medical decisions.
- 10Repeat calculations to track changes over time.
Understanding eGFR
What eGFR tells us about kidney function.
What GFR Measures
GFR = volume of blood filtered by kidneys per minute
Normal GFR: ~120 mL/min/1.73m² in young adults
GFR naturally declines with age (~1 mL/min/year after 40).
Why "Estimated"?
True GFR requires complex tests (inulin clearance). eGFR uses easily measured blood markers (creatinine) with equations validated against true GFR.
Creatinine and GFR
Creatinine is a muscle waste product filtered by kidneys:
- High creatinine → Low GFR (kidneys not filtering well)
- Low creatinine → High GFR (or low muscle mass)
Limitations of Creatinine-Based eGFR
May be inaccurate in:
- Very muscular or very thin patients
- Amputees
- Acute kidney injury (changing rapidly)
- Extremes of age (<18 or >90 years)
- Vegetarian diets
- Creatine supplement users
CKD-EPI 2021 Equation
The current standard for eGFR calculation.
The Formula
For females: eGFR = 142 × min(Scr/0.7, 1)^-0.241 × max(Scr/0.7, 1)^-1.200 × 0.9938^Age × 1.012
For males: eGFR = 142 × min(Scr/0.9, 1)^-0.302 × max(Scr/0.9, 1)^-1.200 × 0.9938^Age
Where Scr = serum creatinine in mg/dL
Key Features
- Race-free (removed race coefficient in 2021)
- More accurate than MDRD at higher GFR
- Validated in diverse populations
- Recommended by NKF and ASN
Why Race Was Removed
The 2021 update removed race from the equation because:
- Race is a social, not biological, construct
- Previous equations may have contributed to healthcare disparities
- Evidence showed race coefficient was not consistently accurate
Comparison with Previous Equations
| Equation | Year | Uses Race | Best For |
|---|---|---|---|
| CKD-EPI 2021 | 2021 | No | General use |
| CKD-EPI 2009 | 2009 | Yes | Historical |
| MDRD | 1999 | Yes | GFR <60 |
CKD Staging
Classifying chronic kidney disease severity.
GFR Categories (KDIGO 2012)
| Stage | GFR (mL/min/1.73m²) | Description |
|---|---|---|
| G1 | ≥90 | Normal or high |
| G2 | 60-89 | Mildly decreased |
| G3a | 45-59 | Mild to moderate |
| G3b | 30-44 | Moderate to severe |
| G4 | 15-29 | Severely decreased |
| G5 | <15 | Kidney failure |
Albuminuria Categories
CKD also staged by urine albumin:
- A1: <30 mg/g (normal)
- A2: 30-300 mg/g (moderately increased)
- A3: >300 mg/g (severely increased)
Complete CKD Classification
Full staging combines GFR (G1-G5) and albumin (A1-A3): Example: "CKD G3aA2" = GFR 45-59 with moderate albuminuria
Prognosis
Lower GFR + higher albuminuria = worse prognosis Green (low risk) → Yellow → Orange → Red (high risk)
Clinical Applications
How eGFR guides medical care.
Drug Dosing
Many medications require adjustment based on eGFR:
| eGFR | Typical Action |
|---|---|
| ≥60 | Usually no adjustment |
| 30-59 | Reduce dose or frequency |
| 15-29 | Further reduction, careful monitoring |
| <15 | May be contraindicated |
Examples: NSAIDs, metformin, certain antibiotics
Monitoring Intervals
| CKD Stage | Recommended Monitoring |
|---|---|
| G1-G2 | Annually |
| G3a | Every 6-12 months |
| G3b | Every 3-6 months |
| G4 | Every 3 months |
| G5 | Monthly or more |
Referral to Nephrology
Consider nephrology referral for:
- eGFR <30 (G4-G5)
- Rapid decline (>5 mL/min/year)
- Significant albuminuria (A3)
- Difficult-to-control hypertension
- Uncertain diagnosis
Dialysis Consideration
Dialysis typically starts when:
- eGFR <10-15 with symptoms
- Symptoms: fatigue, nausea, fluid overload
- Decision is individualized
Factors Affecting Creatinine
Why eGFR may not reflect true kidney function.
High Creatinine (Lower eGFR)
Non-kidney causes:
- High muscle mass (athletes, bodybuilders)
- High meat intake
- Creatine supplements
- Certain medications (trimethoprim, cimetidine)
- Dehydration
Low Creatinine (Higher eGFR)
Non-kidney causes:
- Low muscle mass (elderly, malnourished)
- Amputations
- Vegetarian/vegan diet
- Liver disease (reduced creatine production)
When to Use Cystatin C
Cystatin C is an alternative marker, less affected by muscle:
Use cystatin C when:
- Extreme body composition
- Need confirmation of borderline GFR
- Creatinine may be unreliable
Combined creatinine-cystatin C equations are most accurate.
Acute vs. Chronic
eGFR is for stable kidney function. In acute kidney injury (AKI), creatinine changes rapidly and eGFR is not reliable.
Prevention and Management
Protecting kidney function.
Risk Factors for CKD
- Diabetes (leading cause)
- Hypertension
- Cardiovascular disease
- Family history of kidney disease
- Age >60
- Obesity
- Smoking
Lifestyle Modifications
Dietary:
- Moderate protein intake
- Low sodium (<2,300 mg/day)
- Limit phosphorus and potassium if advanced CKD
- Adequate hydration
Other:
- Regular exercise
- Maintain healthy weight
- Stop smoking
- Limit alcohol
Medications
Blood pressure control is critical:
- ACE inhibitors or ARBs (preferred for CKD)
- Target BP typically <130/80
SGLT2 inhibitors (dapagliflozin, empagliflozin):
- Slow CKD progression
- Benefit extends to non-diabetic CKD
Avoiding Nephrotoxins
- Minimize NSAIDs (ibuprofen, naproxen)
- Avoid IV contrast when possible
- Careful with aminoglycosides
- Avoid herbal supplements with unknown effects
Pro Tips
- 💡eGFR <60 for >3 months indicates chronic kidney disease.
- 💡CKD-EPI 2021 (race-free) is the current recommended equation.
- 💡Normal eGFR decreases with age—about 1 mL/min/year after 40.
- 💡High creatinine = low eGFR, but creatinine reflects muscle mass too.
- 💡Check urine albumin along with eGFR for complete CKD staging.
- 💡Drug dosing often requires adjustment when eGFR <60.
- 💡NSAIDs can worsen kidney function—use cautiously with low eGFR.
- 💡A single abnormal eGFR needs confirmation—repeat in 3 months.
- 💡Cystatin C can provide a second opinion if creatinine is unreliable.
- 💡Blood pressure control is the most important factor for slowing CKD.
- 💡SGLT2 inhibitors protect kidneys even in non-diabetic CKD.
- 💡Report your eGFR to all healthcare providers for safe medication prescribing.
Frequently Asked Questions
Normal eGFR is typically >90 mL/min/1.73m². However, it naturally declines with age—an 80-year-old may have eGFR of 60 without disease. An eGFR >60 with no other signs of kidney damage is often not concerning, but should be monitored.
