eGFR Calculator
Estimate kidney function (eGFR) from a blood creatinine result, age and sex with the race-free CKD-EPI 2021 equation, and see the matching kidney disease stage.
Results
| Item | Value |
|---|
Quick Answer
The CKD-EPI 2021 equation estimates kidney filtering from creatinine, age and sex. A 50-year-old man with creatinine of 1.0 mg/dL has an eGFR of about 92, which is in the normal range (stage G1). An eGFR of 90 or higher is in the normal range, and below 60 for 3 months or more suggests chronic kidney disease.
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Table of Contents
- eGFR Calculator
- Quick Answer
- Related Calculators
- How This eGFR Calculator Works
- How to Use the eGFR Calculator
- Core Formula (CKD-EPI 2021)
- Key Terms
- Worked Example
- Real-Life Examples
- eGFR vs Creatinine Clearance
- Average eGFR by Age
- Kidney Function Stages
- Common Mistakes to Avoid
- Frequently Asked Questions
- References & Sources
How This eGFR Calculator Works
Enter your serum creatinine from a blood test, your age and your sex. The calculator applies the CKD-EPI 2021 equation, which does not use race, and reports your estimated glomerular filtration rate (eGFR) in mL/min/1.73 m². It shows the kidney function stage and the average eGFR for your age group.
Quick explanation: eGFR estimates how much blood your kidneys filter each minute.
- Higher eGFR: better kidney filtering.
- Creatinine: a waste product from muscles that kidneys remove.
- Age: eGFR naturally falls slowly with age.
How to Use the eGFR Calculator
- Find your serum creatinine on your blood test report.
- Choose mg/dL or µmol/L to match the report.
- Enter your age and sex.
- Press Calculate.
- Read your eGFR and stage, and talk to your doctor about what it means for you.
Core Formula (CKD-EPI 2021)
eGFR = 142 × min(Scr ÷ κ, 1)^α × max(Scr ÷ κ, 1)^−1.200 × 0.9938^age × 1.012 (if female)
- Scr: serum creatinine in mg/dL
- κ: 0.7 for females, 0.9 for males
- α: −0.241 for females, −0.302 for males
- µmol/L to mg/dL: divide by 88.4
Key Terms
- eGFR: estimated glomerular filtration rate, a measure of kidney filtering.
- Creatinine: a muscle waste product that healthy kidneys remove from the blood.
- CKD: chronic kidney disease, kidney damage or low function lasting 3 months or more.
- CKD-EPI 2021: a race-free equation recommended to estimate GFR in adults.
- mL/min/1.73 m²: milliliters filtered per minute, adjusted to a standard body size.
Worked Example
A 70-year-old woman has a creatinine of 1.3 mg/dL.
- Scr ÷ κ = 1.3 ÷ 0.7 = 1.857, which is above 1
- eGFR = 142 × 1.857^−1.200 × 0.9938^70 × 1.012
- eGFR ≈ 44, which is stage G3b (moderate to severe)
Real-Life Examples
- Understanding a lab report: a creatinine of 1.0 mg/dL at age 50 for a man is an eGFR of about 92.
- Using µmol/L: 80 µmol/L is about 0.90 mg/dL, so a 40-year-old woman would have an eGFR of about 82.
- Age effect: the same 1.0 mg/dL gives about 104 at age 30 and 78 at age 75 for a man.
- Tracking over time: compare results from several tests, since one value can vary.
eGFR vs Creatinine Clearance
- eGFR: estimated from blood creatinine, age and sex, adjusted to a standard body size of 1.73 m².
- Creatinine clearance: often estimated with the Cockcroft–Gault formula, which also uses weight. Sometimes used for drug dosing.
- Measured GFR: a special test that is more accurate but takes longer.
Average eGFR by Age
| Age | Average eGFR |
|---|---|
| 20 to 29 | 116 |
| 30 to 39 | 107 |
| 40 to 49 | 99 |
| 50 to 59 | 93 |
| 60 to 69 | 85 |
| 70 and older | 75 |
Kidney Function Stages
| Stage | eGFR | Description |
|---|---|---|
| 1 | 90 or above | Possible kidney damage with normal function |
| 2 | 60 to 89 | Kidney damage with mild loss of function |
| 3a | 45 to 59 | Mild to moderate loss |
| 3b | 30 to 44 | Moderate to severe loss |
| 4 | 15 to 29 | Severe loss |
| 5 | Less than 15 | Kidney failure |
Common Mistakes to Avoid
- Using the wrong unit. Check whether your report shows mg/dL or µmol/L.
- Relying on one test. CKD is defined by results that last 3 months or more.
- Testing after heavy exercise or a big meat meal. These can raise creatinine briefly.
- Using it in children. Children need different equations.
- Self-diagnosing. A doctor also looks at urine albumin and other tests.
Frequently Asked Questions
The National Kidney Foundation says 90 or higher is in the normal range. Average eGFR falls with age, to about 75 at age 70 and over.
An eGFR below 60 for 3 months or more, or signs of kidney damage such as protein in the urine, suggests chronic kidney disease.
Below 15, stage 5.
The 2021 CKD-EPI equation was developed without a race variable, and the NKF and ASN recommend it for all adults.
Divide by 88.4. For example, 88 µmol/L is about 1.0 mg/dL.
It can rise if a short-term cause, such as dehydration, is treated. Chronic damage often cannot be reversed, but its progress can often be slowed.
Yes. Very muscular people may get a falsely low eGFR, and people with little muscle a falsely high one.
No. It is for adults 18 and older.
Kidney function naturally declines slowly as people get older.
Often a urine albumin test, blood pressure and blood sugar.
It depends on your health and risk factors. Your doctor will advise you.
No. It is an estimate for information only.
Yes. Being dehydrated can raise creatinine and lower eGFR for a short time. Your doctor may repeat the test once you are well hydrated.
References & Sources
| Source | Used For | Link |
|---|---|---|
| National Kidney Foundation, CKD-EPI Creatinine Equation (2021) | The equation and constants used here. | https://www.kidney.org/professionals/ckd-epi-creatinine-equation-2021 |
| National Kidney Foundation, Estimated GFR (eGFR) | Normal values, average eGFR by age and CKD stages. | https://www.kidney.org/kidney-topics/estimated-glomerular-filtration-rate-egfr |