This sizes water and food to your crew, your days away and the kind of trip you are making, then prints as a checklist you can shop from. The single biggest variable is not appetite, it is whether washing comes out of your tanks.
- Person-days
- Meals to cover
- Shelf-stable meals
- Reserve included
How the Water Figure Is Worked Out
You will see one gallon per person per day quoted a lot. It is worth being clear about what that number is: it is roughly what people manage when they are rationing, not what a crew actually uses on a normal trip.
Reported consumption from cruising boats falls into three bands, and the calculator uses those rather than a single figure:
| What the tanks cover | Per person per day |
|---|---|
| Drinking and cooking only, washing ashore or in salt water | 1.5 to 2 US gallons |
| Drinking, cooking, washing up and navy showers | 4 to 6 US gallons |
| Comfortable use including proper showers | 8 to 12 US gallons |
A navy shower means wetting down, turning the water off while you soap, then a brief rinse. It is the single habit that separates the second band from the third, and it is the reason two boats with identical tankage can have completely different ranges.
For most cruising boats water, not food, is what sets the limit on how long you can stay away. Food can be stacked in lockers. Water is capped by your tanks unless you carry jerry cans or make your own, which is the argument for a watermaker, and the reason a water filter matters when you are filling from a dock hose of unknown quality.
The Weather Reserve
The calculator does not provision for the days you planned. It provisions for those days plus a margin, because the thing that strands people is weather, not hunger.
- Day sailing: no reserve. You are home tonight.
- Coastal cruising with stops: 25%, which covers a couple of days sitting out a blow in the wrong harbour.
- Extended passage with no resupply: 35%, because a slow crossing is normal and there is nowhere to top up.
That reserve is also why at least 30% of the meals come from the shelf-stable store. Those are the meals you will be eating on the days you did not plan for, when the fresh food is gone and nobody wants to cook.
What Actually Constrains Provisioning on a Boat
Storage, not shopping. A supermarket trolley holds more than most 35-foot boats have sensible space for. Lockers are odd shapes, the good ones are under bunks, and anything stored where it can move will find a way to move.
Refrigeration is a power decision. A fridge is one of the largest continuous loads on a cruising boat, so provisioning for a long trip is partly a question of how much you plan to refrigerate. Boats without one lean harder on tins, dried goods and produce that keeps.
Cardboard is a liability. It absorbs damp, it disintegrates in a wet bilge, and it is the classic way cockroaches come aboard. Decant into sealed boxes before you stow.
Things spoil in a predictable order. Soft fruit and salad go first, in days. Hard vegetables like onions, carrots and cabbage last weeks if they are dry and have air around them. Eggs keep for a long time unrefrigerated if they have never been washed, which is common outside the US and not inside it. Plan menus in that order and you waste almost nothing.
Cooking is harder underway than at anchor. The list leans on one-pot meals for that reason. Cooking on a sailboat covers working a gimballed stove in a seaway, and the best food to bring sailing goes deeper on what keeps.
Frequently Asked Questions
Common questions about provisioning a boat:
Does the Water Figure Include Washing Up?
Yes, in the middle and upper bands. The lowest band assumes dishes are done in salt water with a fresh rinse, which is standard practice on boats without much tankage.
Should I Count Bottled Water Separately?
Carry some regardless of tankage. Bottled water is your backup if a tank is contaminated, and it is the only water you can grab if you ever have to leave the boat in a hurry.
How Much Should I Budget for Provisioning?
It varies hugely by cruising ground, since remote islands import everything. The liveaboard budget guide has real monthly food figures, and provisioning for a trip is roughly that rate compressed into one shop.
Is 30% Shelf-Stable Enough for an Ocean Crossing?
It is a floor, not a target. On a long passage most crews end up closer to half, because fresh food runs out in the first week or two no matter how carefully it is stowed.
What About Seasickness in the First Days?
Plan the first 48 hours to need almost no cooking. Crew who are queasy will not eat much, and whoever is not queasy should not be wrestling a pan. Make those meals before you leave.