GFR Calculator: method, checked example and practical limits
Estimate adult eGFR with the race-free 2021 CKD-EPI creatinine equation published by NIDDK. The estimate is normalized to 1.73 square meters of body surface area and is not identical to creatinine clearance in mL/min.
Inputs used by this calculator
GFR Calculator uses the fields below. The starting values reproduce the page example; replace them with values from the same units and time period before using the result.
| Input | Starting example | Accepted value | How it is used |
|---|---|---|---|
| Equation sex | Female equation | Female equation · Male equation | Supplies the equation sex quantity used by the published equation or result breakdown. |
| Age (years) | 55 | 18 to 120 | Supplies the age (years) quantity used by the published equation or result breakdown. |
| Serum creatinine (mg/dL) | 1 | 0.1 to 30 | Supplies the serum creatinine (mg/dl) quantity used by the published equation or result breakdown. |
Inputs and measurement conventions
The quantities used on this page are Equation sex, Age (years), Serum creatinine (mg/dL). Start with values for the same situation and read the units attached to each field. The field reference below shows supported choices and numerical limits.
Acute kidney changes and unusual creatinine production reduce reliability. Diagnosis requires clinical context and often repeat measurements.
Method and equation
Apply the race-free 2021 CKD-EPI creatinine equation using adult age, standardized serum creatinine and the specified sex coefficient.
GFR Calculator uses the following stated relationship: eGFR=142×min(SCr/κ,1)^α×max(SCr/κ,1)^−1.200×0.9938^age×1.012 if female. Its assumptions determine which question the answer can resolve.
eGFR=142×min(SCr/κ,1)^α×max(SCr/κ,1)^−1.200×0.9938^age×1.012 if femaleWorked calculation with the starting values
Equation sex: Female equation; Age (years): 55; Serum creatinine (mg/dL): 1. These starting values give 66.53207791 mL/min/1.73 m² estimated GFR. The calculation breakdown is Creatinine / κ: 1.428571429; κ: 0.7; α: -0.241; Equation sex: female.
Age 55, female equation and creatinine 1.0 mg/dL are evaluated with κ=0.7 and α=−0.241.
Reading the answer
The estimate is normalized to 1.73 square meters of body surface area and is not identical to creatinine clearance in mL/min.
Creatinine / κ: 1.428571429; κ: 0.7; α: -0.241; Equation sex: female. These intermediate quantities make the stated GFR Calculator model inspectable; they should be read together with the main answer rather than treated as independent guarantees.
Common errors and model boundaries
Acute kidney changes and unusual creatinine production reduce reliability. Diagnosis requires clinical context and often repeat measurements.
eGFR is an estimate for adults. NIDDK recommends combined creatinine-cystatin C in situations where accuracy near a decision threshold matters.
Independent verification and next decision
No. Drug labeling, kidney-function method and body-size normalization must be assessed by the prescribing clinician.
For the GFR Calculator method, compare eGFR=142×min(SCr/κ,1)^α×max(SCr/κ,1)^−1.200×0.9938^age×1.012 if female with the starting inputs and the calculation table. The linked NIDDK: race-free eGFR equations for adults and NIDDK: drug dosing and kidney-function estimates references identify the relevant definitions, conventions or domain limitations. Retain intermediate precision when comparing a manually worked answer.
GFR Calculator worked-example ledger
| Quantity | Example value | Role |
|---|---|---|
| Equation sex | Female equation | Entered assumption |
| Age (years) | 55 | Entered assumption |
| Serum creatinine (mg/dL) | 1 | Entered assumption |
| Main answer | 66.53207791 mL/min/1.73 m² estimated GFR | Calculated from the starting inputs |
| Creatinine / κ | 1.428571429 | Intermediate or contextual output |
| κ | 0.7 | Intermediate or contextual output |
| α | -0.241 | Intermediate or contextual output |
| Equation sex | female | Intermediate or contextual output |
Frequently asked questions
Does this determine a medication dose?
No. Drug labeling, kidney-function method and body-size normalization must be assessed by the prescribing clinician.
Which relationship does the GFR Calculator use?
Apply the race-free 2021 CKD-EPI creatinine equation using adult age, standardized serum creatinine and the specified sex coefficient. The displayed relationship is eGFR=142×min(SCr/κ,1)^α×max(SCr/κ,1)^−1.200×0.9938^age×1.012 if female.
What do the starting values produce in the GFR Calculator?
Equation sex: Female equation; Age (years): 55; Serum creatinine (mg/dL): 1. These starting values give 66.53207791 mL/min/1.73 m² estimated GFR. The calculation breakdown is Creatinine / κ: 1.428571429; κ: 0.7; α: -0.241; Equation sex: female.
How should I interpret this GFR Calculator answer?
The estimate is normalized to 1.73 square meters of body surface area and is not identical to creatinine clearance in mL/min.
Which input mistake most affects the GFR Calculator?
Acute kidney changes and unusual creatinine production reduce reliability. Diagnosis requires clinical context and often repeat measurements.
What is outside this GFR Calculator model?
eGFR is an estimate for adults. NIDDK recommends combined creatinine-cystatin C in situations where accuracy near a decision threshold matters.
What to keep in mind
eGFR is an estimate for adults. NIDDK recommends combined creatinine-cystatin C in situations where accuracy near a decision threshold matters.
Results are rounded for display in US format, with money in dollars and cents; CSV exports keep full calculation precision. This is a calculation summary, not an official certificate.