Weigh it, write it, add it back
The single habit that makes rehydrating easy is writing the fresh weight on every bag before the food goes on the tray. Freeze-drying removes water and almost nothing else, so the water to add back is just the fresh weight minus the dried weight. If you package a 300 g portion of chili that dried to 75 g, it needs 225 g of water.
If you didn’t write it down, the food’s typical water content gets you close. The calculator works backward from the dried weight to the fresh weight using USDA water figures and the 3% moisture well-dried food keeps.
Typical water to add per 100 g dried
| Food | Water content | Water per 100 g dried | How |
|---|---|---|---|
| Eggs | 76% | 304 g | Per large egg: about 12 g powder (roughly 2 tbsp) + 38 g water (2½ tbsp). |
| Milk | 88% | 708 g | For 1 cup (244 g) whole milk: about 30 g powder + 214 g water. |
| Chicken | 65% | 177 g | Warm broth or water 10–15 minutes, refrigerated if longer. |
| Ground beef | 58% | 131 g | Cover with hot water or broth 10 minutes. |
| Cooked rice | 68% | 203 g | Boiling water, covered, 5–10 minutes. |
| Potatoes | 79% | 362 g | Hot water 10–15 minutes; fry or bake after. |
| Chili | 77% | 322 g | Boiling water to the original weight, stir, rest 10 minutes. |
| Applesauce | 88% | 708 g | Stir 1 part powder into about 7 parts water by weight. |
Food safety when rehydrating
Freeze-drying does not kill bacteria; they wake up when water comes back. Penn State and Utah State Extension both stress that foods that are normally cooked must still be cooked. If you dried raw eggs or raw meat, cook the rehydrated food to the USDA safe temperature: 160 °F for egg dishes and ground meat, 165 °F for poultry. Rehydrated food is perishable again, so treat it like fresh food and refrigerate leftovers.
Read next
- Making Your Own Freeze-Dried Backpacking Meals: Which home meals freeze-dry and rehydrate well on the trail, how to portion and pack them, how much water each needs, and the fat and safety limits to respect.
Questions people ask
How much water do I add to freeze-dried eggs?
One large egg is about 50 g without the shell and dries to about 12 g. Add back about 38 g of water, roughly 2½ tablespoons, per egg. By volume that is close to 2 tablespoons of powder plus 2½ tablespoons of water.
Hot or cold water?
Hot water speeds up meals, meat and starches. Cold water is better for cottage cheese, fruit you want to stay firm, and anything you will eat cold. Rehydrate meat in the fridge if it will soak more than a short time.
Why add water slowly?
Water content varies a few percent between batches and foods absorb at different speeds. Adding three quarters, waiting, and then topping up avoids soggy results. Utah State Extension specialists suggest starting with a small amount of water and giving it time.
Do I need to rehydrate herbs, onions and peppers?
No. Iowa State Extension notes they can go straight into food and absorb moisture from the dish.
Sources
- Iowa State University Extension AnswerLine: reconstituting freeze-dried foods
- Penn State Extension: Let’s Preserve: Freeze-Drying (usage)
- USDA FoodData Central (water content)
- USDA FSIS: Safe minimum internal temperatures
Figures checked 2026-10-21. How we check them. Spot something off for your machine? Tell us.