How this calculator works
- Pick the household category, enter the water units used, and set the bill period in days.
- The calculator prorates the tariff blocks and service charge from a standard 30-day schedule so shorter or longer bill periods can be estimated.
- Results are shown across three tariff periods to mirror the public comparison style used by Sri Lankan water-bill tools.
Worked example
For 18 units over 30 days on the Domestic tariff, the current estimated bill is LKR 2,116.63.
Important assumptions
- This version focuses on the three household paths shown on the public calculators: Domestic Samurdhi, Non Samurdhi Tenement Garden, and Domestic.
- The current tariff table is modeled from the NWSDB gazette dated August 21, 2024. Numbers.lk labels that same comparison block as 'After Aug 2024' and also shows a January 17, 2025 note, which appears to be a site note rather than a separate published tariff table.
- For the 2023 and 2024 tariff rows, the calculator now shows SSCL and VAT separately. VAT is applied after SSCL, which matches the standard invoice treatment for taxable utilities.
- Official bills can still differ due to arrears, rebates, sewerage, or provider-specific bill adjustments that are outside this simplified calculator.
FAQ
Are these calculators free?
Yes. lankacalculator tools are free to use and designed to be quick to access without sign-up.
How accurate are the results?
The calculators use clear assumptions and formulas, but results are estimates and should be checked against official documents or provider terms.
Can I use this on mobile?
Yes. The layout is built to work cleanly on phones, tablets, and desktops.
Do you store my inputs?
No account is required for these tools, and calculator inputs are not stored as user profiles in this v1 setup.