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Water tank size calculator
A plastic water tank costs Rs 15,500 to 38,700 for 250 gallons and Rs 26,000 to 61,000 for 500 gallons, as of September 2026. Work out the tanks a house needs from the people in it, or what a tank holds, in litres and gallons.
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Calculator
Size your water tanks
Give the people in the house and how many days the water should last, or measure a tank you already have. The answer is in litres and both kinds of gallon.
Tanks for the house
- Overhead tank to buy
- 1,000 litresPlastic, sold as 250 gallons
- Underground tank, inside
- 6 × 3 ftWith 4 ft of water, built in concrete
Where it is kept
- Overhead tankWater for 1 day, 207 imperial gallons
- 940 litres
- Underground tankWater for 2 days, 414 imperial gallons, 66.4 cft
- 1,880 litres
Water a day
- The household6 people at 150 litres
- 900 litres
- Car washing1 car at 40 litres
- 40 litres
- A day
- 940 litres
Plastic tanks are sold by a gallon of about 3.8 litres, close to the US gallon, while building rules count the imperial gallon of 4.55 litres. A full tank weighs a kilogram a litre, so place a roof tank where the engineer says the slab can carry it.
Prices
Water tank price in Pakistan, September 2026
Plastic tanks by the size they are sold as and their grade, which the warranty marks. A 250 gallon (1,000 litre) tank costs Rs 15,500 to 38,700 and a 500 gallon (2,000 litre) one Rs 26,000 to 61,000.
| Sold as | Litres | Economy | Standard | Heavy duty |
|---|---|---|---|---|
| 100 gallons | 400 | None listed | Rs 12,000 to 15,600 | Rs 13,000 |
| 125 gallons | 500 | Rs 8,000 to 14,500 | Rs 10,000 to 13,000 | Rs 13,000 to 18,800 |
| 150 gallons | 600 | Rs 9,500 to 11,000 | Rs 12,000 to 21,000 | Rs 15,400 to 23,100 |
| 200 gallons | 750 | Rs 12,000 to 20,000 | Rs 15,000 to 21,500 | Rs 18,300 to 28,700 |
| 250 gallons | 1,000 | Rs 15,500 to 24,000 | Rs 18,500 to 31,400 | Rs 22,000 to 38,700 |
| 300 gallons | 1,200 | Rs 20,000 | Rs 21,200 to 38,800 | Rs 25,000 to 40,900 |
| 400 gallons | 1,500 | Rs 23,000 | Rs 25,700 to 43,000 | Rs 31,000 to 53,300 |
| 500 gallons | 2,000 | Rs 26,000 to 30,000 | Rs 33,000 to 57,700 | Rs 40,000 to 61,000 |
| 1,000 gallons | 4,000 | None listed | None listed | Rs 97,300 to 120,400 |
| 1,500 gallons | 6,000 | None listed | None listed | Rs 128,800 to 180,300 |
| 2,000 gallons | 8,000 | None listed | None listed | Rs 160,900 to 237,600 |
| 2,500 gallons | 10,000 | None listed | None listed | Rs 191,000 to 307,800 |
Each range runs from the cheapest make to the dearest, at two online sellers in Lahore and one maker's own shop, read on 30 September 2026; the sellers deliver free in Lahore, Rawalpindi and Islamabad, one of them on orders over Rs 12,000. Economy tanks are blow-moulded; standard ones are blow-moulded with 3 to 5 layers or roto-moulded with 2; heavy-duty ones are roto-moulded with 3 layers, heavy blow-moulded, or a maker's premium line. The layers printed on a tank are a maker's label and do not follow the price, so compare the warranty.
Reference
Water tank size by household
The storage a household needs at 150 litres a person a day and 3 days of water, a third of it in the overhead tank, and the plastic tank sizes sold.
| Household | Litres a day | To store, litres | Imperial gallons | Overhead tank to buy | Underground, litres | Underground built, inside |
|---|---|---|---|---|---|---|
| 2 people | 300 | 900 | 198 | 400 litres, 100 gallons | 600 | 3 × 3 ft, 2.5 ft of water |
| 3 people | 450 | 1,350 | 297 | 500 litres, 125 gallons | 900 | 3 × 3 ft, 4 ft of water |
| 4 people | 600 | 1,800 | 396 | 600 litres, 150 gallons | 1,200 | 4 × 3 ft, 4 ft of water |
| 5 people | 750 | 2,250 | 495 | 750 litres, 200 gallons | 1,500 | 4.5 × 3 ft, 4 ft of water |
| 6 people | 900 | 2,700 | 594 | 1,000 litres, 250 gallons | 1,800 | 5.5 × 3 ft, 4 ft of water |
| 8 people | 1,200 | 3,600 | 792 | 1,200 litres, 300 gallons | 2,400 | 6.5 × 3.5 ft, 4 ft of water |
| 10 people | 1,500 | 4,500 | 990 | 1,500 litres, 400 gallons | 3,000 | 7 × 4 ft, 4 ft of water |
| 12 people | 1,800 | 5,400 | 1,188 | 2,000 litres, 500 gallons | 3,600 | 8 × 4 ft, 4 ft of water |
| Sold as | Litres | US gallons | Imperial gallons | Weight full, kg |
|---|---|---|---|---|
| 100 gallons | 400 | 106 | 88 | 400 |
| 125 gallons | 500 | 132 | 110 | 500 |
| 150 gallons | 600 | 159 | 132 | 600 |
| 200 gallons | 750 | 198 | 165 | 750 |
| 250 gallons | 1,000 | 264 | 220 | 1,000 |
| 300 gallons | 1,200 | 317 | 264 | 1,200 |
| 400 gallons | 1,500 | 396 | 330 | 1,500 |
| 500 gallons | 2,000 | 528 | 440 | 2,000 |
| 1,000 gallons | 4,000 | 1,057 | 880 | 4,000 |
| 1,500 gallons | 6,000 | 1,585 | 1,320 | 6,000 |
| 2,000 gallons | 8,000 | 2,113 | 1,760 | 8,000 |
| 2,500 gallons | 10,000 | 2,642 | 2,200 | 10,000 |
The overhead tank is the next plastic size sold that holds a day's water; the underground tank is the inside of one built in concrete with 4 ft of water. Plastic tanks are sold by a rounded gallon name, so check the litres printed on the tank.
Building rules
The smallest tanks Lahore allows
Lahore's building regulations set the least a house may have in each tank, by plot size. Faisalabad's regulations repeat the same table.
| Plot | Underground, inside | Gallons | Litres | Overhead, inside | Gallons | Litres |
|---|---|---|---|---|---|---|
| Up to 7 marla | 6 × 4 × 2.5 ft | 400 | 1,699 | 4 × 3 × 2.5 ft | 200 | 850 |
| 7 marla to 1 kanal | 10 × 5 × 2.5 ft | 800 | 3,540 | 5 × 5 × 2.5 ft | 400 | 1,770 |
| Above 1 kanal | 10 × 5 × 4 ft | 1,200 | 5,663 | 5 × 5 × 4 ft | 600 | 2,832 |
The gallons are the regulations' own, imperial gallons, and the litres are worked from the sizes. Other authorities set their own rules: DHA Islamabad-Rawalpindi, for one, caps a house's overhead tank at 900 gallons up to one kanal and 1,200 above.
How it is worked out
From people to litres and gallons
The calculator adds up the water the house uses in a day: the people at so many litres each, guests and staff at the same, each car at about 40 litres for a bucket wash, and a lawn at about 0.5 litres a sq ft in the hot months. It multiplies that by the days the tanks should last with no supply at all, which is the water to store, and splits it between the two tanks.
How much a person uses depends on how easily water comes. Smart meters in middle and upper income homes in Karachi averaged about 22 gallons a person a day, less than half the 54 gallons the city's water utility plans on, and Islamabad's planners measured about 41 gallons in private houses. WHO counts over 100 litres a person a day in a home with water piped inside. The calculator starts at 150 litres, about 33 imperial gallons; use 100 where water is short and 200 or more where it is plentiful.
The overhead tank feeds the taps by gravity, so it should hold at least a day's water and keep the taps running through a power cut, when the pump cannot fill it. The underground tank takes the supply when it comes, or a tanker load: if you buy water by the tanker, make it big enough for a whole load, and Karachi's utility sells loads of 1,000 to 5,000 gallons. Lahore's building regulations make the overhead tank half the size of the underground one, a third of the water, which is where the calculator starts.
Plastic tanks are made and labelled in litres and sold by a gallon name close to the US gallon of 3.79 litres, which sellers round to 4: a 2,000 litre tank is sold as 500 gallons, though it holds only 440 imperial gallons. Building regulations use the imperial gallon of 4.55 litres, 6.23 to the cubic foot. The calculator gives both and suggests the next plastic size sold for the overhead tank.
An underground tank is usually built in concrete on site, so the calculator also gives its inside size: the litres divided by 28.3 for cubic feet, then by the depth of water for the floor area, about twice as long as it is wide. For a tank you already have, it multiplies the inside length, width and depth of water, or for a round tank 0.785 times the diameter squared times the height of water, and turns the cubic feet into litres and gallons.
On site
Terms you will hear
- Overhead tank
- The tank on the roof, usually plastic, that feeds the taps by gravity. A pump fills it from the underground tank or a bore, and it keeps water in the taps while the power is off.
- Underground tank
- The tank below ground, usually built in waterproofed concrete, that takes the supply line or a tanker load. Building rules want it sealed against seepage and placed so a tanker can fill it from outside.
- Imperial gallon
- 4.546 litres, the gallon Pakistani building rules use: a cubic foot holds 6.23 of them.
- US gallon
- 3.785 litres, about a sixth smaller than the imperial gallon. Plastic tank sizes are close to it: a tank sold as 250 gallons holds 1,000 litres.
- Cft
- A cubic foot, 28.32 litres: the unit a tank built on site is measured and priced in.
- Bowser
- A water tanker, the word DHA's regulations use. They ask for the underground tank to be placed so a bowser can fill it from the road.
Questions
Water tank questions
Still have a question?
Ask our team during Pakistan business hours, in English or Urdu.
+92 333 2466662Chat on WhatsAppWhat is the water tank price in Pakistan?
As of September 2026, a plastic water tank costs Rs 8,000 to 18,800 for 125 gallons (500 litres), Rs 15,500 to 38,700 for 250 gallons (1,000 litres) and Rs 26,000 to 61,000 for 500 gallons (2,000 litres). The price rises with the grade, which the warranty marks: a 250 gallon tank is Rs 15,500 to 24,000 with a 1 to 2 year warranty, Rs 18,500 to 31,400 with 5 years and Rs 22,000 to 38,700 heavy-duty with 7 to 10. Tanks of 1,000 gallons and more are sold only in the heavy-duty grade, Rs 97,300 to 120,400 for 1,000 gallons. The sellers deliver free in Lahore, Rawalpindi and Islamabad, one of them on orders over Rs 12,000; elsewhere, add the delivery.
How much is a 500 gallon water tank?
A tank sold as 500 gallons holds 2,000 litres, about 440 imperial gallons. As of September 2026 it costs Rs 26,000 to 30,000 in the economy grade, with a 1 to 2 year warranty, Rs 33,000 to 57,700 with a 5 year warranty and Rs 40,000 to 61,000 heavy-duty, with 7 to 10 years. Full, it holds 2 tons of water, so it should sit where the engineer says the roof can carry it. A tank that holds 500 imperial gallons, as the building rules count them, is bigger: 2,273 litres.
What size water tank do I need for my house?
Multiply the people in the house by the water each uses a day, add any car washing or lawn, and multiply by the days the tanks should last without supply. A family of 6 at 150 litres each uses 900 litres a day, so 3 days of storage is 2,700 litres (594 imperial gallons): a third of it, 900 litres, in the overhead tank, which a 1,000 litre (250 gallon) plastic tank holds, and 1,800 litres in the underground tank.
How many gallons of water tank does a 10 marla house need?
Take a family of 6 to 8. At 150 litres a person a day and 3 days of storage, 6 people need 2,700 litres (594 imperial gallons) and 8 need 3,600 litres (792 imperial gallons): a 1,000 to 1,200 litre overhead tank, sold as 250 to 300 gallons, and 1,800 litres to 2,400 litres underground. In Lahore the building regulations set the least for a house of 7 marla to 1 kanal at 800 gallons underground and 400 overhead (3,540 litres and 1,770 litres), so build at least that where they apply.
How do I work out the capacity of a water tank in gallons?
Multiply the inside length, width and depth of water in feet to get cubic feet, then multiply by 6.23 for imperial gallons, 7.48 for US gallons or 28.3 for litres. An 8 × 5 ft tank with 4 ft of water holds 160 cft: 997 imperial gallons, 1,197 US gallons or 4,531 litres. For a round tank, multiply the diameter by itself, then by the height of water and by 0.785, to get cubic feet.
Are water tank gallons imperial or US?
Both are in use. Plastic tanks are made in litres and sold by a gallon close to the US gallon, 3.79 litres, which sellers round to 4: a 2,000 litre tank is sold as 500 gallons. Building regulations use the imperial gallon, 4.55 litres, 6.23 to the cubic foot. So a 500 gallon plastic tank holds about 440 imperial gallons, while a tank built to hold 500 imperial gallons holds 2,273 litres.
How big should the underground tank be compared with the overhead tank?
Lahore's building regulations make every house's overhead tank half the size of its underground tank, so a third of the water is overhead: at least 400 gallons overhead and 800 underground for a house of 7 marla to 1 kanal. The overhead tank should hold at least a day's water, so the taps keep running when a power cut stops the pump. If you buy water by the tanker, make the underground tank big enough to take a whole load.
How much water does one person use a day in Pakistan?
It depends on how easily water comes. Smart meters in middle and upper income homes in Karachi averaged about 22 gallons a person a day, less than half the 54 gallons the city's water utility plans on, and Islamabad's planners measured about 41 gallons in private houses. WHO counts over 100 litres a person a day in a home with water piped inside. The calculator starts at 150 litres, about 33 imperial gallons: use 100 where water is short and 200 where it is plentiful.
What size underground water tank should I build?
Divide the litres to keep underground by 28.3 for cubic feet, then by the depth of water for the floor area. For a family of 6 with 3 days of water, 1,800 litres is 63.6 cft, which at 4 ft of water is about 5.5 × 3 ft inside. Leave room above the water for the inlet and overflow, build it in waterproofed concrete, and keep it away from the septic tank: DHA Karachi asks for at least 4 ft between the two.
How much does a full water tank weigh?
A litre of water weighs a kilogram, so a full 1,000 litre tank carries a ton of water and a 2,000 litre (500 gallon) tank two tons, before the weight of the tank. On a roof, that load should sit where the structural engineer says the slab or a beam can carry it.
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