About the 24-Hour Creatinine Clearance Calculator
This tool estimates creatinine clearance from a timed urine collection using serum creatinine, urine creatinine concentration, urine volume, and collection duration. It can help patients, students, and clinicians understand how collection data translates into measured kidney filtration estimates, including a body-surface-area-adjusted result and basic collection-quality flags.
How to use this calculator
- Enter the serum creatinine value and choose mg/dL or µmol/L.
- Enter the urine creatinine concentration and choose mg/dL or mmol/L.
- Enter the total urine volume in mL and the actual collection duration in hours.
- Select the reference range sex, then enter height in cm and weight in kg for BSA correction.
- Click Calculate to view clearance, corrected clearance, urine flow, and creatinine excretion.
- Click Reset to restore the default example values.
How it works
The calculator first converts serum creatinine and urine creatinine into matching mg/dL units if needed. Urine flow rate is calculated as total urine volume divided by the collection time in minutes.
Creatinine clearance is calculated as urine creatinine multiplied by urine flow rate, divided by serum creatinine. The result is reported in mL/min. Body surface area is estimated with the Mosteller formula, then clearance is adjusted to a standard 1.73 m² using measured clearance × 1.73 ÷ BSA.
The calculator also estimates daily creatinine excretion from the urine creatinine concentration and total volume, then scales it to mg/kg/day. It compares corrected clearance and excretion per kg with broad adult screening ranges based on the selected sex; these are not diagnostic by themselves.
Results are educational estimates and not medical advice. Accuracy depends on a complete timed urine collection, stable kidney function, lab methods, muscle mass, diet, medications, pregnancy status, and clinical context.
Example calculation
Using the default values: serum creatinine 1.00 mg/dL, urine creatinine 100 mg/dL, urine volume 1,500 mL, collection duration 24 hours, male, height 170 cm, and weight 70 kg. Urine flow is 1,500 ÷ 1,440 = 1.04 mL/min, so creatinine clearance is 100 × 1.04 ÷ 1.00 = 104.2 mL/min. BSA is about 1.82 m², so the BSA-corrected clearance is 104.2 × 1.73 ÷ 1.82 = about 99.0 mL/min/1.73 m². Daily creatinine excretion is 1,500 mg/day, or 21.4 mg/kg/day.
Frequently asked questions
What is a 24-hour creatinine clearance test used for?
It estimates how much creatinine the kidneys clear from the blood, which can provide a measured estimate of kidney filtration when a timed urine collection is available.
Does the collection have to be exactly 24 hours?
No. The calculator uses the actual collection duration in hours and adjusts the urine flow rate, but accuracy still depends on collecting all urine during the timed period.
Why is BSA-corrected creatinine clearance different from measured clearance?
Measured clearance reflects the patient’s actual body size. BSA-corrected clearance scales the result to a standard 1.73 m² body surface area so it can be compared more easily with broad reference ranges.
What does low creatinine excretion per kg suggest?
A low value can suggest under-collection, low muscle mass, or other clinical factors. It should be interpreted with a healthcare professional rather than used alone.
Is creatinine clearance the same as eGFR?
No. Creatinine clearance is calculated from urine and blood measurements, while eGFR is usually estimated from blood creatinine plus demographic variables. They may differ, especially if the urine collection is incomplete or muscle mass is unusual.