How much drinking water
for your household?
Estimate a baseline and compare it with what you have. This calculator does not estimate all household water use.
Current Be Ready guidance and PDF checklist checked 27 October 2026.
2 people × 3 litres × 3 days. Drinking water only. Current Be Ready drinking-water baseline; see methodology below.
Methodology: a calculation you can check
The current Be Ready drinking-water baseline is people × 3 litres × days. For four people over three days: 4 × 3 × 3 = 36 litres. If 24 litres are already stored, the gap is max(0, 36 − 24) = 12 litres. Excess stored water never produces a negative gap.
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What this estimate includes—and leaves open
Current Be Ready guidance specifies 3 litres per person per day for drinking. Its downloadable checklist uses the same figure. Count each person once, including infants; this does not determine infant-feeding or clinical requirements. Individual needs, weather and activity can change requirements.
Allow separately for cooking, hygiene, pets, infant feeding and medical needs. Those needs vary, so this calculator does not invent numerical allowances. Seek suitable professional advice for feeding and medical arrangements.
Why do some sources say 2.5–3 litres or 10 litres?
The earlier Prepare guidance described a 2.5–3 litre survival drinking range and a larger 10-litre allowance including basic cooking and hygiene. The current Be Ready checklist specifically uses 3 litres for drinking. We use the current figure and leave additional requirements separate; 36 litres for four people is not an estimate of all water use.
Compare the official Be Ready PDF checklist. Sources were checked on 27 October 2026; revisit the current guidance when planning.
Water quality matters as well as quantity
Follow your water supplier’s instructions for your area. Different notices can require different action. Boiling and ordinary filters do not remove every contaminant. See the water supply planning guide for context and official source links.
Sources and next steps
Check official UK preparedness guidance and your local water supplier before relying on an estimate. The editorial policy records the review limitations. This independent product is not endorsed by the government.
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