PrepSources and method
Every figure on this site comes from a named source. Advice changes, so each tool shows when it was last checked.
All figures were last checked on 2 November 2026.
How much water do official sources say to store?
There's no single figure, because they measure different things. Always look at what a number covers.
| Source | Figure | Covers | For how long |
|---|---|---|---|
| UK government, Be Ready | 3 litres a person a day | Drinking only | 3 days |
| British Red Cross | About 10 litres a day | With basic cooking and washing | 3 days |
| Ready.gov (US) | 1 gallon (3.8 L) a person a day | Drinking and sanitation | Several days |
| CDC (US) | 1 gallon (3.8 L) a person a day | Not split | 3 days; 2 weeks if possible |
| Germany, BBK | 2 litres a person a day | Drinking, plus 0.5 L cooking | 10 days ideal |
| Sweden, MCF | 3 to 5 litres an adult a day | Drinking, cooking, basic hygiene | At least a week |
How the calculators work
Each tool explains its own method. The days-ready calculator uses the same sums as the Prep app: 2,000 kcal and 3 litres for an adult, 1,600 kcal and 2 litres for a child, and 1 litre for a pet. These are planning figures, not nutritional advice.
Calories per pack combine USDA FoodData Central figures per 100 g with typical pack sizes, which we chose. Labels vary, so they're estimates.
Independence
We don't take affiliate commission or sponsorship and don't sell supplies. The site promotes our own app, Prep. It isn't connected to any government, charity or retailer, and nothing here is official advice.
Licences
Contains public sector information licensed under the Open Government Licence v3.0. US federal information is credited to the agency that published it. Food energy data: U.S. Department of Agriculture, FoodData Central.
UK sources
- Age UK: prepare for a storm
- Arab News (press report, 23 October 2026): UK government on Be Ready
- Assimilated Regulation (EU) No 1169/2011, Annex X (legislation.gov.uk)
- Be Ready checklist (PDF)
- Be Ready household emergency plan (PDF)
- Be Ready: advice for disabled persons and carers
- Be Ready: be informed about hazards
- Be Ready: be ready for emergencies
- Be Ready: cold weather, snow and ice
- Be Ready: fires in the home
- Be Ready: flooding
- Be Ready: hazardous substance and radiation exposure
- Be Ready: hot weather and heatwaves
- Be Ready: phone and broadband outages
- Be Ready: power cuts
- Be Ready: storms
- Be Ready: water supply interruptions or outages
- Blue Cross: preparing for a flood with your pet
- Breastfeeding Network: emergency checklist for families with a young baby
- Breastfeeding Network: feeding your baby in an emergency
- British Red Cross: how to prepare your home for 72 hours
- British Red Cross: prepare an emergency kit
- CDC (US): carbon monoxide poisoning
- CDC (US): how to create an emergency water supply
- CDC (US): what to do during a power outage
- CDC: making water safe in an emergency
- Centre for Sustainable Energy: how much electricity am I using?
- Citizens Advice: prepare for a power cut
- Drinking Water Inspectorate: receiving a boil water notice
- Energy Networks Association: compensation for power cuts
- Energy Networks Association: what to do if you have a power cut
- FAA PackSafe: working out watt-hours
- FEMA and American Red Cross: Food and Water in an Emergency (PDF)
- Food Standards Agency: food fact checker
- Food Standards Agency: food safety in a power cut
- Food Standards Agency: home food fact checker
- Food Standards Agency: how to chill, freeze and defrost food safely
- Food Standards Scotland: flooding (refreezing)
- Food Standards Scotland: power cuts
- FoodSafety.gov (US): food safety during a power outage
- Generac: GP series brochure
- German Federal Office of Civil Protection: guide to emergency preparedness (PDF)
- GOV.UK: avoid and report internet scams and phishing
- GOV.UK: beat the heat
- GOV.UK: best before and use-by dates
- GOV.UK: expiry date for confusing date labels (2011)
- GOV.UK: households encouraged to take small, simple steps
- GOV.UK: Report Fraud, new service from City of London Police
- GOV.UK: selling, buying and carrying knives
- ITV News (press report, 22 October 2026): Streeting urges public to prepare
- LBC (press report, 27 October 2026): supermarket shelves after Be Ready
- Met Office
- Mississippi State University Extension: does honey go bad?
- National Grid: priority services
- NHS: burns and scalds
- NHS: carbon monoxide poisoning
- NHS: foods to avoid giving babies and young children
- NHS: how to make up a bottle feed
- NHS: hypothermia
- NHS: understanding calories
- NI Direct: care registers
- NI Water: Customer Care Register
- nidirect: energy, power supply and utilities (gas emergency number)
- NIE Networks: Customer Care Register
- Ofgem: compensation for energy supply issues
- Ofgem: join your supplier's Priority Services Register
- Ofwat: supply interruptions
- PDSA: flood safety for pets
- Phoenix Energy: contact us
- Priority Services Register
- Public Health England: government dietary recommendations (2016, PDF)
- Ready.gov: power outages
- Ready.gov: water
- RSPCA: keeping animals safe during floods
- SACN: dietary reference values for energy (2011, PDF)
- SGN: power cuts
- St John Ambulance: first aid consumables, questions and answers
- St John Ambulance: first aid kits for emergency situations
- St John Ambulance: first aid kits, questions and answers
- St John Ambulance: first aid supplies FAQs
- St John Ambulance: what to put in a first aid kit
- Swedish Civil Defence and Resilience Agency: home preparedness
- Swedish Civil Defence and Resilience Agency: In case of crisis or war
- The Highway Code: breakdowns and incidents
- UK Chief Medical Officers: food and nutrition scripts for a national power outage
- UK Chief Medical Officers: keeping warm or cool, scripts for a national power outage
- UK Chief Medical Officers: water and sanitation scripts for a national power outage
- UK Health Security Agency: how to recover from flooding
- UK Health Security Agency: minimum water requirements, a rapid evidence summary (PDF)
- UK Health Security Agency: what to do in a radiation emergency
- UK Public Survey of Risk Perception, Resilience and Preparedness 2026
- US EPA: emergency disinfection of drinking water
- USDA FoodData Central
- USDA FoodKeeper data
- USDA FSIS (US): freezing and food safety
- USDA FSIS (US): shelf-stable food safety
- Utility Regulator: additional services
- Water UK: technical guidance note 11
- West Berkshire Council: animal welfare during emergencies
US sources
- American Red Cross: make a first aid kit
- American Red Cross: survival kit supplies
- CDC: carbon monoxide poisoning
- CDC: emergency list for families with infants and young children
- CDC: frequently asked questions about radiation emergencies
- CDC: how to create an emergency water supply
- CDC: keep food safe after a disaster or emergency
- CDC: making water safe in an emergency
- CDC: potassium iodide (KI)
- CDC: preparedness and safety messaging for hurricanes, flooding and similar disasters
- CDC: preparing for a hurricane
- CDC: preparing for a winter storm
- CDC: preventing botulism
- CDC: what to do to protect yourself during a power outage
- Centre for Sustainable Energy: how much electricity am I using?
- CPSC safety alert: portable generator hazards
- CPSC: what to know about generators
- Dietary Guidelines for Americans, 2025 to 2030 (PDF)
- EPA: emergency disinfection of drinking water
- FAA PackSafe: working out watt-hours
- FDA: are you storing food safely?
- FDA: food and water safety during power outages and floods
- FDA: how to cut food waste and maintain food safety
- FDA: infant formula safety do's and don'ts
- FEMA and American Red Cross: Food and Water in an Emergency (PDF)
- FEMA: Are You Ready?, appendix B
- FoodSafety.gov: food safety during a power outage
- Generac: GP series brochure
- HRSA: Poison Help
- Mississippi State University Extension: does honey go bad?
- National Weather Service: hurricane supplies
- OSHA: using portable generators safely
- Ready.gov: build a kit (July 1, 2026)
- Ready.gov: car safety
- Ready.gov: Disaster Preparedness Guide for Older Adults
- Ready.gov: emergency alerts (May 27, 2026)
- Ready.gov: family emergency communication planning (PDF)
- Ready.gov: food (March 12, 2026)
- Ready.gov: hurricane season toolkit
- Ready.gov: hurricanes
- Ready.gov: low and no cost ways to prepare
- Ready.gov: make a plan (September 1, 2026)
- Ready.gov: older adults
- Ready.gov: power outages
- Ready.gov: prepare your pets for disasters
- Ready.gov: radiation emergencies (January 7, 2025)
- Ready.gov: safety skills
- Ready.gov: water
- Ready.gov: winter weather
- USDA FoodData Central
- USDA FoodKeeper data
- USDA FSIS: a consumer's guide to food safety, severe storms and hurricanes
- USDA FSIS: food product dating
- USDA FSIS: freezing and food safety
- USDA FSIS: shelf-stable food safety (October 24, 2024)
Changes
- 2 November 2026: site launched. UK figures follow the Be Ready campaign, launched 22 October 2026.