How to use the dehydrating yield calculator
- Choose whether to find the dried weight from a fresh weight, or the fresh weight needed for a dried weight you want.
- Enter the weight, then the moisture when fresh and the moisture after drying, as percents of the weight at each stage.
- Pick a unit label. The unit is only a label; the result uses the same unit as the input.
- Read the weight, the water removed and the dry solids, which stay constant.
Formula
dry solids = fresh weight x (1 - fresh moisture)
dried weight = dry solids / (1 - final moisture)
water removed = fresh weight - dried weight
Drying removes water and leaves the solids behind, so the solids weigh the same before and after. The last line of the steps checks that the moisture left matches your target.
A kilogram of fresh apple slices
Fresh slices weigh 1,000 g and are 85% water, so the dry solids weigh 1,000 x 0.15 = 150 g. If you dry them to 20% moisture, the dried weight is 150 / 0.80 = 187.5 g. That removes 812.5 g of water, so the slices lose 81.25% of their weight and you need 5.33 g of fresh food for each gram of dried.
In the other direction, to end with 200 g at 10% moisture from food that starts at 88% water, the solids are 180 g and the fresh weight is 180 / 0.12 = 1,500 g.
Where the moisture numbers come from
Fresh moisture varies by variety, ripeness and how a food is cut. Use a value for your own food, from a reliable nutrition table or from weighing a sample before and after drying. The target moisture depends on the food and the storage plan, and this page does not say what is dry enough.
Planning a batch
Use the fresh-weight mode to plan how much produce to buy or pick for a target amount of dried food. The yield per gram of fresh food also helps when you compare unit prices for fresh and dried products with the Unit Price Calculator. To scale ingredients up or down, see the Recipe Scaler.
Assumptions and limits
- Moisture is the share of water in the total weight at that stage.
- Only water leaves. Oils and sugars that drip away are not modeled.
- The unit is a label. Grams, kilograms, ounces and pounds all give the same ratios.
- Food safety, drying time and temperature are not covered. Follow a tested method.
Frequently asked questions
Why must the final moisture be lower than the starting moisture?
Drying removes water, so the food cannot end wetter than it started. If you enter a higher final value, the page asks you to correct it instead of showing a negative loss.
How do I find the moisture of my food?
Weigh a sample fresh, dry it fully, and weigh it again. The weight lost divided by the fresh weight is the moisture share. Reliable food composition tables also list the usual water content of many foods.
Is a lower final moisture always better?
Not necessarily. Some foods need to stay a little pliable, and others need to be crisp. The right target depends on the food and how you plan to store it.
Does the unit change the result?
No. The unit is only a label for your input. The percent weight loss and the ratio of fresh to dried food are the same in any unit.