Hydraulic Retention Time (HRT) Calculator
Calculate detention time from tank volume and flow, or size required volume for a target HRT. Enter your design or operating values below for an instant engineering estimate with the governing formula shown on the page.
Educational estimate. Calculator results are for planning and information only, not financial, tax, medical, legal, or engineering advice. Verify important decisions with official sources or a qualified professional.
Hydraulic Retention Time (HRT) Calculator
Wastewater Engineering Calculator
📐 Formula & Method
Detention Time
Rearrange to V = Q × HRT when sizing a tank for a target detention time.
📋 How to Use
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Enter the design or operating flow, concentration, or geometry inputs.
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Confirm units shown beside each field (typically m³/h, mg/L, m²).
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Click Calculate to view results and verify against your design criteria.
Hydraulic Retention Time (HRT) Calculator for STP & ETP Design
Calculate detention time from tank volume and flow, or size required volume for a target HRT.
This calculator is part of the CalculatorsHive STP & ETP hub. Results are planning-level estimates — confirm with local design standards, pilot testing, and equipment vendor data before final design.
🔬 Methodology & Accuracy
Formula: Standard wastewater engineering formula implemented client-side with SI units.
Data sources: Metcalf & Eddy Wastewater Engineering; EPA design manuals; standard activated sludge and clarifier sizing practice.
Last reviewed: July 2026 · General formula used: Detention Time · Accuracy: Results are precise to two decimal places using IEEE-754 double-precision arithmetic. Intended for educational and planning use only.
For informational purposes only. Results are estimates based on the inputs and formulas provided. For financial, tax, medical, or legal decisions, consult a qualified professional. Rates and regulations change — always verify current figures with official sources.