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Price per litre against tap
Turning a bottle price and a water bill into one comparable figure is arithmetic, not opinion. Here is the calculation, a table of price per litre at common bottle sizes, and a calculator for your own numbers.
The two calculations
Bottled water. Price per litre = bottle price ÷ bottle size in litres. That is the whole thing. The reason it is worth doing explicitly is that shelf prices are quoted per bottle and per pack, in sizes from 0.33 to 5 litres, which makes the per-litre figure genuinely hard to see.
Tap water. Price per litre = price per cubic metre ÷ 1 000. Household water bills in Estonia, Finland and Latvia are metered per cubic metre, and almost always carry two rates: one for supplying clean water and one for taking the wastewater away. Both are charged on the same metered volume, so the honest cost of a litre out of the tap is the sum of the two divided by a thousand. Some bills also carry a fixed monthly charge, which does not change with volume and so does not belong in a per-litre comparison.
The ratio between the two is the number people actually want. Divide the bottled figure by the tap figure. Because one is priced per bottle and the other per thousand litres, the answer is normally three or four orders of magnitude — but it is your bill and your shelf, so use your own two numbers.
Price per litre at common bottle sizes
Read down for the price you paid, across for the bottle size. Every cell is simply the price divided by the litres, computed on the server.
| Price paid | 0.33 l | 0.5 l | 0.75 l | 1 l | 1.5 l | 5 l |
|---|---|---|---|---|---|---|
| 0.30 per bottle | 0.91 | 0.60 | 0.40 | 0.30 | 0.20 | 0.06 |
| 0.50 per bottle | 1.52 | 1.00 | 0.67 | 0.50 | 0.33 | 0.10 |
| 0.70 per bottle | 2.12 | 1.40 | 0.93 | 0.70 | 0.47 | 0.14 |
| 0.90 per bottle | 2.73 | 1.80 | 1.20 | 0.90 | 0.60 | 0.18 |
| 1.20 per bottle | 3.64 | 2.40 | 1.60 | 1.20 | 0.80 | 0.24 |
| 1.50 per bottle | 4.55 | 3.00 | 2.00 | 1.50 | 1.00 | 0.30 |
| 2.00 per bottle | 6.06 | 4.00 | 2.67 | 2.00 | 1.33 | 0.40 |
| 3.00 per bottle | 9.09 | 6.00 | 4.00 | 3.00 | 2.00 | 0.60 |
Your own numbers
Enter what you actually pay and how much you actually drink. Nothing is sent anywhere; the calculation runs in your browser, and the table above still works if you would rather not use it.
Enter your figures to see the price per litre, the cost of a year, and the multiple against tap.
What the ratio does and does not settle
It settles the money and nothing else. Bottled water buys three things a tap does not: a mineral profile you can choose deliberately, a taste you may prefer, and portability. If you are drinking a high-magnesium water because of the magnesium figure, or a very-low-mineral water because of a specific reason to want one, then the comparison with tap water is not really a like-for-like comparison at all.
Two costs sit outside the per-litre figure. Packaging and transport are the obvious one — a litre of water weighs a kilogram and most of it is moved a long way. The other is deposit-return: in Estonia, Finland, Latvia and Lithuania the bottle carries a deposit which comes back when you return it, so the shelf price overstates the true cost slightly if you actually return your bottles, and understates the hassle if you do not.
And one thing the arithmetic cannot tell you: whether the water from your own tap is hard, soft, high in nitrate or anything else. That is per-waterworks information, published by your local utility, and it is the number you would need before deciding that the tap is the right comparison in the first place.
Analyses: the figures each producer publishes on the label or in its technical sheet — see the basis line on every water page. Reference intakes: EFSA Dietary Reference Values. Label claims: Directive 2009/54/EC, Annex III. Mineral-water constituent limits and the fluoride labelling rule: Directive 2003/40/EC. Tap-water parametric values: Directive (EU) 2020/2184. Checked 2026-09-06.
Frequently asked questions
How do I work out the price per litre of bottled water?
Divide the price by the number of litres. A 1.5 litre bottle at 0.90 is 0.60 per litre; a six-pack of 0.5 litre bottles at 2.40 is three litres, so 0.80 per litre. Multipacks are not automatically cheaper per litre, which is the whole reason to do the division.
How much does tap water cost per litre?
Take the price per cubic metre from your water bill and divide by 1 000, because a cubic metre is 1 000 litres. Most household bills charge separately for supply and for wastewater, and both are billed on the metered volume, so add the two rates together before dividing.
How much more expensive is bottled water?
Divide your bottled price per litre by your tap price per litre. Because tap water is billed per cubic metre and bottled water per bottle, the ratio is normally in the hundreds or thousands rather than in single digits. Use your own two numbers rather than a figure from an article.
Is bottled water worth it?
That depends on what you are buying it for. A specific mineral profile — very low mineral content, high magnesium, low sodium — is something tap water cannot be chosen for. Taste and convenience are real too. What the arithmetic does is put a number on what those preferences cost per year, so the decision is made with the figure visible.
All waters compared
The full analysis table, grouped by mineral content.
Water hardness explained
Degrees, millimoles and parts per million, converted, plus what hardness does and does not do.
Low-sodium water
The 20 mg per litre label rule, and how much sodium a litre of each water really carries.
Water highest in magnesium
Every water ranked by magnesium, against the EFSA adequate intake.
Water highest in calcium
Calcium per litre ranked, and how much of a day it covers.
Bicarbonate and alkaline water
What bicarbonate is, which waters carry a lot of it, and what it comes packaged with.
The habit is the expensive part, not the bottle
TempoLife shows what you actually drink over a month, which is usually a different number from the one you would have guessed.