This tool is for preparing in advance. If your water is already off, contaminated, or under a boil-water notice, follow your water company's current instructions — they are the primary source of information during an outage. Find your supplier →
WaterReady.co.uk
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Free · No account needed · Based on UK government guidance

Be ready when your water supply isn't.

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≈ 9L min / 3 days Drinking water only, at the UK minimum-survival rate of 3L per person per day. Doesn't include hygiene, medical needs or activity — the full calculator below covers those. Updates automatically as you fill in the questionnaire.
Calculate
Progress 0% complete
Your household
Everyone this water plan needs to cover.

The under-12-months cut-off for babies matches NHS guidance on sterilising feeding equipment — it's the age where that changes.

Dehydration risk rises with age — thirst sensation and kidney function both decline, and some medications increase fluid loss. It's worth planning toward the comfortable amount rather than the minimum, and checking for available support.

These increments follow EFSA's dietary reference values for water and are added automatically to your total.

Based on UK veterinary guidance (Hill's Pet UK cites a normal range of 25–50mL/kg/day; UK veterinary practices commonly reference a textbook range of 20–70mL/kg/day for dogs) of roughly 40mL/kg/day for dogs and 35mL/kg/day for cats. This is a general starting point, not a substitute for vet advice — actual needs vary with diet, activity, heat and health.

Medical & Additional Needs
Does anyone in your household...

Ready-to-feed formula is preferable when water can't be boiled and bottles can't be sterilised. Plan quantities around your child's normal needs and current NHS guidance — this calculator won't estimate that figure for you.

Contact your care team to establish this figure and what to do during an outage — we won't estimate it. See examples of what counts

For example: home dialysis, oxygen therapy, wound care, or feeding tubes.

We won't estimate this figure — it depends on your specific equipment. Ask your specialist nurse, consultant, or equipment provider directly. If you're not sure who to ask, the equipment's user manual or the supplier's patient support line (often printed on the device or your prescription paperwork) should have this information.

Where do you live?
So we can point you to the right official contacts.

Auto-suggested based on your city — water company boundaries don't always match town boundaries exactly, so double-check and change this if it's not right for your address.

How many days are you planning for?
This is the biggest single factor in how much water you'll need overall.
What season are you planning for?
Heat can significantly increase how much water your household needs.

Heat significantly increases water needs — it's worth planning toward the comfortable figure rather than the minimum, and considering extra for hydration.

Activity
Exercise and hard physical work increase how much water you need.

Non-drinking water
Washing, cleaning and flushing — kept separate from your drinking water above.

Planning for a week or more brings in needs that don't really apply to a few days — laundry is the clearest example, so it's worth accounting for separately here.

The default here is a low, conservation-minded starting point for hand-washing — there's no reliable general figure for hand-washing specifically, so adjust it based on how you'd actually do it. If you'll have a working machine and mains water access, a UK machine cycle averages roughly 50L (modern machines typically use 45–55L) — increase it to that if so.

Where you live

Free things to do now
  • Check the best-before date on any stored water and rotate it as instructed.
  • Keep water away from chemicals and direct sunlight.
  • Save your water company's contact number somewhere offline.
  • Make a plan for babies, pets and medical equipment specifically.
  • Check on relatives or neighbours who might need support.
  • Label which containers hold drinking water and which don't.
Your water plan
2 adults · 3 days
You currently have 0 L of suitable bottled water stored.
Minimum 3L/person/day Comfortable 10L/person/day
Drinking water
0% 0%
Litres needed — —
You currently have L
Gap remaining — —
Non-drinking water rough estimate Washing, cleaning & flushing. Unlike the figures above, there's no official UK or WHO number for this — treat it as a rough starting point, not a target. For longer stays, actual use tends to sit toward the higher end of this range, as pure conservation (sponge-bath level) gives way to wanting a proper wash.
— —
You currently have L
Litres needed — —
Gap remaining — —
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Minimum Requirements For All
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x140 Kirkland Water (500ml)

Drinking
x140 Kirkland Water (500ml)x140 Kirkland Water (500ml), single bottle

Purpose: cover your minimum drinking-water gap without a large storage footprint. 140 x 500ml bottles of natural spring water.

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Inpress Plastics 5L Water Container

Drinking
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x10 Vira Safe Hand Sanitiser (500ml)

Hygiene
x10 Vira Safe Hand Sanitiser (500ml)x10 Vira Safe Hand Sanitiser (500ml), 3-pack view

Purpose: basic hygiene cover when water is limited, per government guidance. 70% alcohol, UK-made, contains Vitamin E and Aloe Vera.

★★★★★ 4.5 out of 5 (818 ratings)

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We recommend

Edena 100L Space Saver Water Butt

Non-drinking
Edena 100L Space Saver slimline water butt with integrated tap, lid and stand

Purpose: a genuine rigid, permanent non-drinking reserve rather than an emergency-only container. 100 litre slimline water butt with an integrated tap, lid and stand, plus a diverter kit to connect to your existing downpipe and start collecting rainwater automatically.

★★★★★ 4.5 out of 5 (150+ ratings)

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Ad: This page contains affiliate links. We may receive a commission if you purchase through them, at no extra cost to you. Product recommendations are commercial suggestions and are not endorsed by the UK Government or your water supplier.
How the numbers work

How much water do you actually need in a drought or supply interruption?

There's no single official water-storage figure, because it depends on how many people you're planning for and how long you want to cover. UK government guidance gives two reference points instead: a minimum of 2.5–3 litres per person per day for drinking, and roughly 10 litres per person per day for a more comfortable amount that also covers basic cooking and hygiene.

This calculator takes those two figures and applies them to your actual household — adults, children, babies, pets, and anyone with medical equipment — so instead of a generic number, you get a plan sized to your home, plus what you're still missing.

It's designed to encourage steady, sensible preparation rather than panic buying: check what you already own, store water safely, and top up gradually. During an actual outage, your water company is the best source of live information — this tool is for getting ready beforehand, not for responding to a supply that's already off.

Search terms this page is built to answer: water usage calculator, how much water do I need in a drought, emergency water storage UK, how much water should I store per person.

Worked examples by household size

A few common household combinations, calculated using the same 3L and 10L per person per day figures as the calculator above — useful as a quick reference even before you fill anything in.

HouseholdPlanning periodMinimum planComfortable plan
1 person1 day3 litres10 litres
1 person3 days9 litres30 litres
2 people3 days18 litres60 litres
4 people5 days60 litres200 litres
5 people7 days105 litres350 litres
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Common questions

FAQ

How much water do I need per person per day in an emergency? Sourced

A minimum of 2.5 to 3 litres of drinking water per person per day, or around 10 litres per person per day for a more comfortable amount including basic cooking and hygiene.

How much water should I store for a drought or water outage in the UK?

It depends on your household size and how many days you're preparing for — this calculator works it out for you using the government's minimum and comfortable figures.

Can I drink water from a water butt in an emergency? Non-drinking

No — it may contain bacteria or disease. It's fine for non-drinking uses like flushing the toilet, but keep it clearly separate from your drinking water.

Is this an official government tool?

No. It's an independent calculator that applies published UK government figures to your household. Always follow your water company's instructions during an actual live outage.

See the full FAQ →

↑ Back to the calculator
Where these figures come from

Official sources

UK-wide

Disclaimer: This calculator provides general guidance based on published UK government figures, for planning purposes only. It does not replace advice from your water supplier, local authority, GP, vet, or care team, and it is not a substitute for following official instructions during a live emergency. See our full terms & disclaimer.

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