Septic Tank Sizing
Tank capacity, dimensions and soak pit sizing per IS 2470.
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Enter your values, then press Calculate Now to evaluate the output.
Guide — Septic Tank Sizing
The septic tank calculator below follows standard Indian construction practice and the relevant IS-code conventions. Enter the site dimensions exactly as measured, press Calculate Now, then refine the quantities line by line in the live sheet before you export.
IS 2470 sizes a septic tank from the daily sewage flow multiplied by the detention period, plus a sludge storage allowance based on the desludging interval — typically two years for a domestic tank.
Keep the length-to-width ratio between 2:1 and 4:1 and the liquid depth between 1.0 m and 2.0 m. Add 300 mm of freeboard above the liquid level and provide a baffle wall at one-third of the length.
The effluent still needs disposal. A soak pit or dispersion trench must be sized from the percolation rate of the soil and kept at least 15 m away from any drinking water source.
Treat every output as an indicative pre-tender estimate. Site conditions, wastage allowances, specification changes and local market rates all move the final figure, so validate against your drawings and approved rate analysis before procurement.
Master Measurement Sheet
| Sr. No. | Description | Unit | NOS 1 | NOS 2 | L | B | D | QTY | Action |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 1.000 |
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About the Septic Tank Sizing
This tool is built for site engineers, quantity surveyors, contractors and property investors who need dependable numbers fast. Every input is reactive — changing a single field instantly recomputes the full output set, so you can run sensitivity checks on dimensions, grades and rates before committing to an estimate.
Keep unit consistency in mind: metric inputs (metres, square metres, cubic metres) produce metric outputs, with imperial and Indian trade units shown alongside where they are commonly used on site.