Free tools
STP and RO capacity calculator
Get a quick, realistic estimate of the plant size your site needs, then let our engineers confirm it.
- Based on common Indian norms
- Instant result
- Engineer verification
How the estimate works
Sewage treatment plants in India are usually sized in KLD (kilolitres per day). The starting point is daily water demand, which is commonly estimated from per-person norms used in Indian design practice, for example around 135 litres per person per day for residences and about 45 litres per person per day for offices. Typically 80 to 90 percent of that water returns as sewage.
Our calculator applies these norms and adds a design margin. Real loads vary with occupancy patterns, fixtures and climate, so treat the result as a planning figure. Before you buy, an engineer should confirm the capacity, peak flows and effluent quality.
STP capacity calculator
What size STP does your building need?
Based on water-demand norms commonly used in India, with a design margin.
Assumes about 85% of water supplied becomes sewage. An engineer will confirm peak flow and effluent quality.
Get a quote for this sizeRO capacity calculator
How big should your RO plant be?
Enter how much treated water you need each day and how many hours the plant can run.
Indicative only. Feed water TDS, temperature and pre-treatment change the final design.
Get a quote for this sizeTypical water demand norms used for sizing
Indicative figures commonly used in India. Your consultant or local authority may specify different values.
| Building type | Typical water demand |
|---|---|
| Residential (with full flushing) | ~135 L per person per day |
| Offices | ~45 L per person per day |
| Day schools | ~45 L per person per day |
| Hotels | Higher; calculated per bed/room |
| Hospitals | Higher; calculated per bed |
| Restaurants | Calculated per seat |
FAQs: STP Capacity Calculator
Straight answers to what clients ask us most. Can't find yours? Ask us directly.
Still have a question?
Talk to an engineer: +91 90734 97917 or WhatsApp us. You can also email contact@bjc-global.com.
Why add a margin to the calculated capacity?
Occupancy grows, usage peaks on weekends and holidays, and equipment ages. A sensible margin, typically 10 to 20 percent, avoids an overloaded plant that fails discharge norms. Oversizing too much wastes capital and can make biological treatment unstable, so an engineer should fine-tune it.
Is the calculator result enough to buy a plant?
No. It is a planning estimate. A proper design also considers peak flow, sewage strength, space, discharge or reuse standards and local requirements. Share your calculator result with us and we will confirm the right capacity.
How do I convert KLD to litres per hour?
1 KLD is 1,000 litres per day. If the plant treats water evenly over 24 hours, 1 KLD is about 42 litres per hour. For RO plants, capacity is usually expressed in LPH based on the hours the plant actually runs each day.
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Want an engineer to check your number?
Send us your calculator result and site details for a free capacity check and quote.