# Renal Clearance Calculator (C = U·V/P) Compute renal clearance C = U × V / P with direct or timed-collection urine flow, interpreted against GFR ≈ 125 mL/min (reabsorption / inulin-like / secretion). Not medical advice. > Canonical page: https://elysiatools.com/en/tools/renal-clearance-physiology - **Category:** Health - **Keywords:** renal clearance, clearance formula, inulin clearance, gfr, urine flow, plasma concentration, tubular reabsorption, tubular secretion, kidney physiology, nephrology ## Overview The Renal Clearance Calculator computes the renal clearance of any filtered substance using the classic physiological formula C = (U × V) / P. It accepts direct urine flow rates or computes flow from timed collection volumes, then compares the calculated clearance against a standard glomerular filtration rate (GFR ≈ 125 mL/min) to determine whether the substance undergoes net tubular reabsorption, filtration without modification, or net tubular secretion. ## Inputs - **Urine Flow Input** (select): Enter urine flow V directly, or derive it from a timed urine collection (volume ÷ duration). - **U — Urine Concentration (mg/mL)** (number): Urine concentration U of the substance. Must use the same units as plasma P (they cancel). - **P — Plasma Concentration (mg/mL)** (number): Plasma concentration P of the substance. Must use the same units as urine U. - **V — Urine Flow Rate (mL/min)** (number): Urine flow rate V in mL/min (used when flow input mode is selected). - **Timed Urine Volume (mL)** (number): Total urine volume collected (used in timed mode). - **Collection Duration (min)** (number): Collection duration in minutes (used in timed mode). - **Decimal Places** (number) ## When to use - Analyzing renal clearance in medical physiology coursework or kidney function problem sets. - Evaluating whether an endogenous or exogenous substance exhibits net tubular secretion or net reabsorption. - Converting timed urine collection data into standardized clearance rates in milliliters per minute. ## How it works - Select the urine flow input method: enter a known flow rate (mL/min) or enter timed urine collection volume (mL) and duration (min) to calculate flow. - Enter the substance concentration in urine (U) and plasma (P) using matching concentration units. - The tool computes clearance using C = (U × V) / P and calculates the clearance fraction relative to standard GFR (125 mL/min) to categorize tubular handling. ## Use cases - Physiology students verifying inulin clearance calculations to understand GFR measurement principles. - Researchers assessing para-aminohippurate (PAH) clearance data from timed urine samples to evaluate tubular secretion. - Instructors generating nephrology problem set examples showing glucose or urea reabsorption ratios. ## Frequently asked questions ### What units should be used for urine and plasma concentrations? You can use any concentration unit (such as mg/mL or mmol/L) as long as urine (U) and plasma (P) use the exact same units, allowing them to cancel out. ### What does a clearance equal to 125 mL/min indicate? A clearance of approximately 125 mL/min matches standard GFR, indicating the substance is freely filtered at the glomerulus and neither reabsorbed nor secreted (inulin-like handling). ### What does it mean if clearance is higher than 125 mL/min? A clearance significantly greater than GFR indicates net tubular secretion, where additional substance is actively secreted from peritubular capillaries into the renal tubule (such as PAH). ### How does timed collection mode derive urine flow rate? In timed mode, the calculator divides the total collected urine volume (in mL) by the duration (in minutes) to determine the urine flow rate V in mL/min. ### Is this calculator intended for clinical diagnostic decisions? 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