Nairobi Water Bill Calculator

Background.

If your Nairobi Water meter moved 18 units last month, you used 18 cubic metres: 18,000 litres, or 900 twenty-litre jerricans. At the domestic rates set up here, that water costs KSh 1,428, and if the house is on the sewer line a further KSh 835.50 is added for sewerage, making KSh 2,263.50 before any fixed charges or arrears. None of those figures is units times a single price, and seeing how they are built is the quickest way to check a bill or plan for a bigger household.

Nairobi City Water and Sewerage Company bills in blocks. The first 6 cubic metres each month are charged at the lowest rate, KSh 68 per cubic metre in the default schedule, and only the water above that pays the next rate, KSh 85, up to 20 cubic metres. Using more never re-prices the water you have already used; it only changes the rate on the extra. Sewerage follows the same pattern on a smaller volume. Sewage is not metered, so the bill assumes 75% of the water you draw goes down the drain and charges that volume at KSh 58 per cubic metre for the first 6 and KSh 65 after.

The structure produces two different prices for the same month. Spread over all 18 cubic metres, the bill averages KSh 125.75 per cubic metre. The next cubic metre, though, costs KSh 133.75: KSh 85 for the water plus 75% of KSh 65 for the sewer. That marginal figure, about KSh 2.68 a jerrican, is what a running cistern, a visiting relative or a long session with the garden hose actually adds.

The default rates are the ones in NCWSC's approved tariff gazette dated 27 February 2026, issued under the oversight of the Water Services Regulatory Board (WASREB), which approves and gazettes water tariffs across Kenya. Tariffs are revised from time to time, so every rate and the first-block limit is an editable field; if your bill or a newer gazette shows different figures, type those in. What no tariff can show is your account history. Arrears, credits, deposits, reconnection fees, penalties and estimated readings live on the statement, and you add them by hand if you want the full amount due.

What is nairobi water bill calculator?

A Nairobi water bill is the sum of a progressive water charge on metered consumption, a progressive sewer charge on an assumed share of that consumption, and any fixed charges and account adjustments. Consumption is measured in cubic metres (1 m³ = 1,000 litres), which is what the meter records and what the bill counts as units.

A tariff block is a band of consumption with its own price per cubic metre. Increasing-block billing means each band's rate applies only to the cubic metres that fall inside it, a design regulated water tariffs commonly use to keep a basic quantity of water affordable while heavier use pays more per unit. The sewer volume factor turns water in into wastewater out: with the default 75%, 18 m³ of water becomes 13.5 m³ of billable sewage, which then goes through its own blocks.

Because the blocks and the sewer charge both scale with the same meter reading, the bill grows slightly faster than consumption. For a sewer-connected home on the default rates, the average cost per cubic metre is KSh 111.50 for a 6 m³ month, KSh 121.75 at 12 m³ and KSh 125.75 at 18 m³. A household that is not on the sewer pays the water charge alone, so the same 18 m³ averages KSh 79.33.

How to use this calculator.

1. 01Enter the month's consumption in cubic metres, which is the current meter reading minus the previous one on your bill. If you think in litres, divide by 1,000; fifty 20-litre jerricans make one cubic metre.
2. 02Check the water block limits and rates against your latest bill or the current gazetted tariff. The defaults are the domestic rates from the 27 February 2026 tariff: KSh 68 per m³ up to 6 m³, then KSh 85 per m³ for everything above that. These are domestic rates; for another type of account, replace the first-block limits and the rates with the schedule on your bill.
3. 03Set Sewer connected to No if the house drains to a septic tank or soak pit. Otherwise leave it on Yes and confirm the sewer factor (75% by default) and the two sewer blocks, KSh 58 and KSh 65 per m³.
4. 04Put any fixed monthly charge shown on your bill into Fixed monthly charges, and enter arrears as a positive amount or a credit as a negative amount under Prior balance or adjustment.
5. 05Compare the water and sewer charges line by line with the bill. The average per cubic metre includes fixed charges and adjustments, so leave those at zero when you want the pure cost of the water itself.

The formula.

For each band with lower limit L₍ᵢ₋₁₎, upper limit Lᵢ and rate rᵢ, the cubic metres billed in that band are min(V, Lᵢ) − L₍ᵢ₋₁₎, never less than zero, and the water charge is the sum over the bands of band volume × band rate. With the default rates and V above 6 m³, that reduces to 6 × 68 + (V − 6) × 85. The sewer volume is S = V × factor ÷ 100, and the sewer charge runs the same band arithmetic on S with the sewer rates. The total is water + sewer + fixed charges + adjustments, and the average charge per cubic metre is that total ÷ V.

Because sewage is billed on 75% of the water, its bands change at different meter readings from the water bands. The sewer volume only passes 6 m³ when water use passes 8 m³,. So the price of one more cubic metre steps up in stages: KSh 68 + 0.75 × 58 = KSh 111.50 up to 6 m³ of water, KSh 85 + 0.75 × 58 = KSh 128.50 between 6 and 8 m³, and KSh 85 + 0.75 × 65 = KSh 133.75 above that.

Two simplifications are worth knowing before you rely on a figure. Only two rates can be entered for water and two for sewer, with one limit between them, and all consumption above that limit is charged at the second rate. If the gazetted schedule for your category has a further, dearer band at higher consumption, an estimate for heavy use will come out low, and the gap will show when you compare it with the bill. There is no customer-class setting: whatever rates sit in the fields are what get charged. The calculation also takes the consumption as one month's figure, so a bill covering a longer reading period may not match exactly.

A worked example.

Frequently asked questions.

References& sources.

1. [1]Nairobi City Water and Sewerage Company (2026). Nairobi Water Approved Tariff Gazette Vol. 34, 27 February 2026. NCWSC.
2. [2]Water Services Regulatory Board (2026). Gazetted Tariff. WASREB.
3. [3]Water Services Regulatory Board (2024). Tariff Guidelines 2024. WASREB.
4. [4]Nairobi City Water and Sewerage Company (n.d.). Home. NCWSC.
5. [5]National Institute of Standards and Technology (2026). NIST Handbook 133, Appendix E: General Tables of Units of Measurement. U.S. Department of Commerce.