Emergency Kit Quantity Calculator for Your Household

Start with 72 hours, then decide what yours is for

Three days is the standard first target because it matches the realistic gap between a disruption starting and organised relief arriving. That is the window almost every emergency agency plans around. A 72-hour kit is small enough to assemble in a month of ordinary shopping. It is cheap enough that no household has a genuine excuse. It is complete enough to survive a storm outage, a water main break or an evacuation notice. It is also the kit that gets stress-tested by real life. A power cut that lasts a night teaches your family the layout of the torches and the taste of the emergency food without any drama.

Beyond 72 hours, the design question changes. A week or more of sheltering at home favours big static volumes: barrels of water and pantry-depth food. The normal household rhythm then powers down to essentials. Evacuation-readiness instead favours weight: what two hands can carry to a car in ninety seconds. Many households end up with three layers - the 72-hour grab kit, the deeper home stores behind it, and a car box. The calculator output is the shopping list for whichever layer you are building. Run it once per layer, and the overlap becomes obvious.

• 72 h: the standard first kit, sized for evacuation or short outages
• 7 days: shelter-in-place territory - add stored water depth and food variety
• 14+ days: beyond a kit; this is household stockpiling and needs a resupply plan

The maths behind every quantity

Consumables follow the rate model. Water sits at four litres per person per day. Ready-to-eat food runs at roughly three meals per person per day, plus hygiene allowances that assume no showering. Four people for three days therefore wants 48 litres of water and 36 meal portions. Those numbers feel startling until they are itemised: twelve two-litre bottles and a case of tinned meals. At that point the kit becomes a supermarket trip rather than a project. Non-perishable extras - biscuits, dried fruit, chocolate - are caloric insurance rather than meals. Every plan also benefits from a few morale items that cost nothing to carry.

Durables do not scale with days at all, which is the part lists-of-nouns always blur. The durables list is short: two torches with spare batteries, a crank or battery radio, and a whistle per person. Add one manual can opener, blankets or thermal blankets one per person, and a basic multitool. Power banks go in charged to 60-80% for storage, and documents sit in one waterproof pouch. These are bought once and live in the kit indefinitely; only the consumables need rotating. The practical result is simple. The first build costs the most. Every later 'refill to days-of-cover' pass is just water, food and batteries - a routine, not an event.

Adjusting the output for your actual household

The calculator models a generic adult; real households deviate in predictable directions. Infants add formula and water far above the baseline, plus nappies. Elderly members may add medication, mobility aids and glasses. Pets add their own water, food and a lead. Prescription-dependent members need a rotating buffer of whatever cannot be bought in an emergency. Climate pushes the whole list sideways. Cold climates weight it toward warmth and insulation. Hot ones weight it toward water and shade. Any flood risk puts the entire kit on a raised shelf or in the car, not in the hallway cupboard.

Treat the output as the floor and these adjustments as the difference between a kit and your kit. The standard method is a two-column audit. Print the calculated list, then walk your household adding the personal items beside it. Check both columns against the three scenarios you actually face where you live. Fifteen minutes with a clipboard produces a more honest plan than another purchase. It is also the audit that reveals the torch that has been 'coming tomorrow' for three years.

Maintaining the kit so it still works in year three

Kits fail quietly. Batteries corrode and water plastic ages through. Sun cream and meds pass their dates. The power bank you stored full self-discharges to nothing over a year. The fix is a rotation calendar rather than vigilance. Put consumables on a six-month taste-and-date check. Top up or replace batteries and power banks annually. Refresh water on its container schedule. Everything else can ride the annual weekend when smoke alarm batteries get changed anyway - one reminder to run the whole system. Store the list itself inside the kit, updated with the year, so the next person knows what should be there.

The second failure mode is access. A well-maintained kit can sit locked in the loft or in a car that is not at home. A box labelled so generic that nobody opens it fails the same way. Kit placement is part of the design. Keep it on the ground floor, with one labelled location per layer. Every household member should know where the keys live, and a duplicate list belongs in the documents pouch. If an outage starts at 2am, one person should be able to reach the plan in the dark. A yearly fire drill builds that habit better than any product purchase.

Accuracy, assumptions and limitations

This is a quantities tool, not a competence tool. It assumes water was treated or verified potable when packed. It assumes ready meals genuinely need no cooking or refrigeration. It assumes the durable gear works on the day it is needed. Each assumption deserves a live check. It does not size anything for children below the standard adult consumption band. It does not model fuel, heating or sanitation beyond the basics. It also cannot know your local risks. A bushfire, flood or earthquake kit shares this core but diverges in the specific layers.

Where it fits better is as the first arithmetic pass of a wider plan. Run the numbers, then shop the list. After that, read the corresponding guides: water storage and purification, power and lighting, and the full household emergency plan. Those guides handle the judgement calls that multiplication cannot. The estimate's real job is to convert 'we should probably have a kit' into a specific list, a specific shelf and a specific rotation date. At that point preparedness stops being a feeling and starts being inventory.