Dehydrating Time Calculator
Get the temperature, time range and expected dried yield for dehydrating a food.
Dehydrating fails quietly at the two ends: food pulled too early moulds in the jar, and food left too long turns to scented cardboard. This calculator gives the standard temperature and time range for twenty common foods, adjusts for slice thickness, and estimates the dried yield from your fresh weight, because 10 lb of apples becoming a pound and a half of chips surprises everyone once.
Times assume a fan dehydrator with the food in a single layer. Your machine, your humidity and your slicing hand all move the finish; the doneness tests in the notes are the real answer, and the clock is the guide.
How this is worked out
Each food carries its standard dehydrator temperature and time range at the standard slice thickness (about a quarter inch unless the prep note says otherwise). Time scales roughly with the square of thickness in drying theory; the factors used here (0.75 for thinner, 1.4 for thicker) are the practical kitchen version of that rule. Dried yield assumes the food loses about 85 percent of its weight as water, true within a few points for most fruits and vegetables; herbs lose nearer 90 percent, and jerky nearer 60 to 70.
Assumptions:
- A fan dehydrator holding its set temperature. Oven drying on a warm setting runs slower and less evenly; add a third to the times and prop the door for moisture escape.
- Single layers with air gaps. Stacked or overlapping pieces dry at the pace of the slowest layer.
- Conditioning (resting dried food in a jar for a week, shaking daily) is part of the process for fruit; it evens residual moisture before storage.
Worked examples
1. Ten pounds of apple slices at 1/4 in. 135 F for 6 to 12 hours, and about 1.5 lb of chips out. The shrinkage is why dried fruit is priced as it is.
2. Tomato slices before a camping trip. 145 F, 8 to 14 hours, until leathery to crisp. Slices dried crisp keep months and powder beautifully for soups.
3. A glut of zucchini, sliced thin. At the thinner setting, about 5 to 9 hours at 125 F. Seasoned before drying, the chips are the one zucchini glut solution that takes no freezer space.
Temperatures at a glance
| Food group | Setting | Doneness test |
|---|---|---|
| Herbs | 95 F | Leaves crumble between fingers |
| Vegetables | 125 F | Brittle or leathery per type; no cool moist centre |
| Fruits | 135 F | Leathery, pliable, no moisture bead when squeezed |
| Tomatoes, onions | 145 F | Leathery to crisp |
| Meat jerky | 160 F | Bends and cracks without snapping; follow USDA guidance |
Higher is not faster in any useful sense: case hardening (a dry shell over a wet centre) is what happens when the temperature outruns the moisture’s path out, and it is the main cause of mouldy jars.
Common mistakes
- Uneven thickness. A tray of mixed slices finishes across a four hour spread. Slice with a mandoline or a steady hand and sort the tray once mid-dry.
- Judging while warm. Warm dried fruit feels pliable and moist; the same piece cooled is crisp information. Always test a cooled piece.
- Skipping conditioning for fruit. A week in a jar, shaken daily, equalises moisture between pieces and reveals any wet batch (condensation on the glass) while it can still go back into the dryer.
- Dehydrating onions and fruit together. Onions perfume everything in the machine and the house. Strong flavours dry alone, ideally outdoors or in a garage.
Putting the result to work
Label jars with the food, the date, and the fresh weight that went in; the yield ratio tells you next year how much fresh glut a jar represents. Store cool and dark, and check fruit jars in the first week for condensation. Gluts worth planning for are exactly what the Crop Yield Calculator predicts, so a big expected harvest can meet a ready dryer rather than a surprised one.
How long does dehydrating take?
- Pick the food; its temperature and time range at standard thickness are built in.
- Adjust for your slice thickness if it differs from about a quarter inch.
- Optionally enter the fresh weight to see the expected dried yield.
- Dry in a single layer and start testing pieces (cooled) at the early end of the range.
- Condition fruit in a jar for a week before long storage.
How do I know when dehydrated food is done?
By the food, cooled: fruit leathery and pliable with no moisture beading from a torn edge; vegetables brittle or crisp; herbs crumbling; jerky bending with cracks but not snapping. Time ranges get you to the testing window; the tests decide. When in doubt, dry longer: over-dried food stores safely and rehydrates, under-dried food moulds.
Why did my dried fruit mould in the jar?
Almost always residual moisture: pieces dried unevenly, judged warm, or packed without conditioning. The fix is process, not temperature: even slices, cooled tests, and a week of conditioning in the jar with daily shaking, watching for condensation, before the food goes to the pantry.
What temperature should I dehydrate at?
By food group: herbs about 95 F to keep their oils, vegetables about 125 F, fruits about 135 F, and meat jerky 160 F with the meat first heated to 160 F internally per USDA guidance. One temperature for everything is the most common beginner error; the groups genuinely differ.
How much weight does food lose when dried?
Most fruits and vegetables lose 80 to 90 percent of their weight, because that share of them is water: 10 lb of apples gives roughly 1.5 lb of chips. Herbs lose nearer 90 percent. Jerky loses less, about 60 to 70 percent, which is why dried meat stays substantial.
Can I dehydrate in an oven instead?
Yes, at its lowest setting with the door propped open for moisture to escape, accepting slower and less even drying (add about a third to the times, and rotate trays). Foods dry best between 95 and 160 F; ovens that cannot go below 170 F will case harden fruit and cook herbs rather than drying them.
Temperatures, times and doneness tests follow standard dehydrator manufacturer and US extension food preservation guidance. Jerky follows USDA food safety recommendations.
