Calculate Glomerular Filtration Rate (GFR) for adults and children using multiple validated formulas. Assess kidney function and chronic kidney disease stages with detailed analysis.
Glomerular Filtration Rate (GFR) describes the rate of flow of filtered fluids through the kidney and is used as a measure of kidney function. Generally, a higher value of GFR indicates better kidney function. A significant decrease in GFR indicates that the kidney is not properly functioning, resulting in lower volumes of fluids being filtered over a given time.
The normal range of GFR adjusted for body surface area is 100 to 130 mL/min/1.73m² in men and 90 to 120 mL/min/1.73m² in women below the age of 40. After age 40, GFR decreases progressively with age.
Where SCr = serum creatinine in mg/dL
More accurate than MDRD, especially at higher GFR levels
If SCr < 0.8 mg/dL, use 0.8 mg/dL for SCr
Used for children 18 years and younger
| Age | Mean Estimated GFR (mL/min/1.73 m²) |
|---|---|
| 20-29 | 116 |
| 30-39 | 107 |
| 40-49 | 99 |
| 50-59 | 93 |
| 60-69 | 85 |
| 70+ | 75 |
| Stage | GFR Value (mL/min/1.73 m²) | Description | Clinical Action |
|---|---|---|---|
| Normal | 90+ and no proteinuria | Normal kidney function | Screening, CKD risk reduction |
| CKD Stage 1 | 90+ with kidney damage | Kidney damage with normal GFR | Diagnosis and treatment, CVD risk reduction |
| CKD Stage 2 | 60-89 with kidney damage | Mild decrease in GFR | Estimating progression |
| CKD Stage 3 | 30-59 | Moderate decrease in GFR | Evaluating and treating complications |
| CKD Stage 4 | 15-29 | Severe decrease in GFR | Preparation for kidney replacement therapy |
| CKD Stage 5 | <15 | Kidney failure | Kidney replacement (if uremia present) |
Kidney Function Assessment: GFR is the best overall measure of kidney function. It helps determine how well the kidneys are filtering waste and excess water from the blood.
Disease Staging: GFR values are used to stage chronic kidney disease, helping guide treatment decisions and monitoring disease progression.
Drug Dosing: Many medications require dose adjustments based on kidney function. GFR helps healthcare providers prescribe safe and effective medication doses.
Treatment Planning: GFR values help determine when to start specific treatments, such as preparing for dialysis or kidney transplantation.
Blood Pressure Control: Maintaining normal blood pressure (less than 130/80 mmHg) helps protect kidney function and slow progression of kidney disease.
Diabetes Management: Keeping blood sugar levels well-controlled reduces the risk of diabetic kidney disease and protects existing kidney function.
Healthy Lifestyle: Regular exercise, maintaining a healthy weight, not smoking, and limiting alcohol consumption all support kidney health.
Medication Awareness: Avoiding overuse of NSAIDs (like ibuprofen) and being cautious with other potentially nephrotoxic medications helps preserve kidney function.
Regular Monitoring: Regular check-ups including blood pressure, blood sugar, and kidney function tests help detect problems early when treatment is most effective.
To calculate GFR (glomerular filtration rate), you need your age, gender, race, and serum creatinine level from a blood test. Our GFR calculator uses the CKD-EPI equation, the most accurate method recommended by medical professionals. For example, a 45-year-old white female with creatinine 1.0 mg/dL has an estimated GFR of approximately 78 mL/min/1.73m². Normal GFR is 90-120 mL/min/1.73m². According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), GFR is the best overall indicator of kidney function. Monitor other health metrics with our BMI calculator and blood pressure calculator.
A low GFR indicates reduced kidney function and possible chronic kidney disease (CKD). GFR below 60 mL/min/1.73m² for 3+ months suggests CKD. Stages include: Stage 1 (GFR 90+, normal with kidney damage), Stage 2 (60-89, mild reduction), Stage 3 (30-59, moderate reduction requiring treatment), Stage 4 (15-29, severe reduction needing specialist care), Stage 5 (below 15, kidney failure requiring dialysis/transplant). The National Kidney Foundation provides comprehensive GFR interpretation guidelines. A GFR of 45 means kidneys function at only 45% capacity. Calculate related health risks with our diabetes risk calculator.
eGFR (estimated GFR) is calculated using formulas based on creatinine levels, age, gender, and race, while true GFR requires complex procedures measuring actual kidney filtration. For practical purposes, eGFR provides sufficient accuracy - within 10-15% of measured GFR for most patients. Our calculator provides eGFR, which doctors use for CKD diagnosis and monitoring. Both methods measure kidney filtration in mL/min/1.73m². The CKD-EPI equation used by our calculator is more accurate than older MDRD formula, especially for GFR above 60. Learn about kidney health through CDC kidney disease resources.
Serum creatinine is the primary factor in GFR calculation - higher creatinine indicates lower kidney function. Normal creatinine ranges: men 0.7-1.3 mg/dL, women 0.6-1.1 mg/dL. Creatinine of 1.5 mg/dL in a 60-year-old male yields GFR around 50 mL/min/1.73m² (Stage 3 CKD), while 3.0 mg/dL might indicate GFR of 20-25 (Stage 4). Factors affecting creatinine include muscle mass, diet (high protein increases it), medications, and hydration status. The relationship is inverse and non-linear: small creatinine increases significantly reduce GFR, especially at higher baseline levels. Calculate other medical values with our body surface area calculator and ideal weight calculator.
GFR monitoring frequency depends on CKD stage and rate of decline. Stage 1-2 CKD: annually if stable. Stage 3: every 6-12 months. Stage 4-5: every 3-6 months or more frequently. Diabetics and those with hypertension should check GFR at least annually regardless of current function. If GFR declines more than 5 mL/min/year, increase monitoring frequency. According to Mayo Clinic CKD guidelines, regular GFR tracking helps detect progression early and adjust treatment. Use our GFR calculator between doctor visits to track trends, but always confirm with laboratory testing.
GFR can improve in some cases, especially if kidney damage is acute (sudden) rather than chronic. Acute kidney injury from dehydration, infections, or medications may recover with proper treatment - GFR could increase 20-40 points. However, chronic kidney disease progression is usually irreversible; treatment focuses on slowing decline rather than reversing damage. Early-stage CKD patients (GFR 60-89) managing diabetes and blood pressure well may stabilize GFR for years. Average CKD progression is 2-5 mL/min/year decline, but some patients remain stable decade or more. Lifestyle changes (diet, exercise, medication compliance) significantly impact progression rate. Monitor health trends with our comprehensive health calculator.
Beyond creatinine, GFR calculation incorporates age (GFR naturally declines 1 mL/min/1.73m² per year after age 40), gender (men typically have 15-20% higher GFR than women due to muscle mass), and race (historically, Black patients had adjustment factor, though this is now reconsidered). Other factors not in the formula but affecting actual kidney function include: hydration status, medications (especially ACE inhibitors, ARBs), protein intake, muscle mass, pregnancy, and acute illness. For most accurate results, get creatinine tested when well-hydrated, fasting, and at least 24 hours after strenuous exercise. The NIDDK CKD guidelines recommend considering these factors in clinical interpretation.
Consult a nephrologist (kidney specialist) when: GFR falls below 30 mL/min/1.73m² (Stage 4 CKD), GFR declines rapidly (more than 5 mL/min/year), GFR below 60 with complications (anemia, bone disease, electrolyte imbalances), or difficult-to-control blood pressure/diabetes with kidney involvement. Many primary care doctors manage Stage 1-3 CKD, but specialist care improves outcomes for advanced disease. Early referral (GFR 30-45) allows time for treatment planning, potential transplant evaluation, and dialysis preparation if needed. Nephrology consultation is also warranted for unexplained GFR decline in young patients (under 50) or when GFR doesn't match clinical picture. Calculate specialist visit timing and plan healthcare with our medical planning calculator.