Food Dehydration Time Calculator

How this food dehydration time calculator works

Home dehydrators remove moisture from food using a gentle flow of warm, dry air. The exact time it takes is hard to predict because it depends on water content, slice thickness, temperature, air flow, and humidity. This calculator uses a simple physics-based model to give you a ballpark estimate of drying time and final dried weight for fruits, vegetables, herbs, and meats used for jerky.

The model assumes that water moves from the center of each slice to the surface, then evaporates into the moving air. Foods that hold onto water strongly (like sugary fruits or dense meats) dry more slowly, while thin leafy herbs dry quickly. The calculator captures these differences with a constant for each food type and adjusts the time based on your chosen slice thickness and temperature.

Formula used for the drying time estimate

The drying time estimate is based on the following relationship:

t = k × d × (Tref / T)α

• t = estimated drying time (hours)
• k = drying constant for the selected food type (hours per millimetre)
• d = slice thickness (millimetres)
• T = dehydrator temperature (°C)
• T_ref = reference temperature (fixed at 60 °C in this model)
• α = temperature sensitivity exponent (dimensionless)

In plain language, the time increases in proportion to thickness and decreases as you raise the temperature. A higher temperature means a smaller ratio Tref / T, which reduces the total time when raised to the power α. Lower temperatures reverse this effect and make drying slower.

Typical drying constants and moisture loss by food type

Each food type uses a different constant k and a typical moisture loss percentage. These values are averages drawn from common dehydrating practice and are not specific to any one variety or recipe.

The moisture loss percentage describes how much of the water is removed by the end of drying under typical conditions. The calculator uses this to estimate your final dried weight from the starting weight you enter.

Interpreting the results

When you submit the form, the calculator returns:

• Estimated drying time: a range or single value in hours based on the formula above.
• Estimated final dried weight: your starting weight minus the typical moisture removed for that food type.

These values are intended as planning tools, not precise predictions. Use them to decide when to start a batch, how to stagger multiple loads, or how many jars or bags you might need once everything is dry.

Worked example

Imagine you want to dry apple slices for snacks:

• Food type: fruit
• Slice thickness: 5 mm
• Temperature: 60 °C
• Starting weight: 500 g

For fruit, the model uses k = 1.1 hr/mm. At the reference temperature of 60 °C, the temperature factor is 1, so the time is roughly:

t ≈ 1.1 × 5 × (60 / 60)α = 5.5 hours

The typical moisture removed for fruit is about 80%. If 80% of the original weight is water that is driven off, the final dried weight is roughly:

Final weight ≈ 500 g × (1 − 0.80) = 100 g

The calculator performs these steps for you automatically and displays both the time estimate and the expected final weight.

You can repeat the process for other foods. For example, for herbs cut into small pieces at 40 °C, the lower k value and higher moisture loss will lead to a short drying time and a very light final weight. Jerky made from 4 mm slices at 70 °C will show a much longer time, and the model keeps more mass in the final product because meat does not dry to the same extent as fruit or herbs.

Factors that affect real-world drying time

The model is intentionally simple, so many real-world factors can make your actual results faster or slower than the estimate:

• Humidity and room temperature: In a humid or cool room, the air entering the dehydrator already holds more moisture, so evaporation slows down.
• Dehydrator design and air flow: Models with stronger fans and better air channels dry more evenly than small stackable units with weak circulation.
• Load size and tray spacing: Overfilled trays, overlapping pieces, or blocked vents can all extend drying time significantly.
• Slice size and uniformity: Very thick or irregular pieces will dry unevenly, leaving some parts too wet while others are over-dry.
• Food variety and sugar/fat content: Different varieties of apples, tomatoes, or meats behave differently, even at the same thickness and temperature.

Because of these variables, always treat the calculator output as an estimate and rely on physical checks for doneness before storing food for more than a short period.

Limitations and food safety notes

This tool is designed for planning and educational use. It does not verify that food is safe to eat or store long term. Keep the following in mind:

• Approximate times only: The formula does not account for your specific dehydrator model, local climate, or exact recipe. Actual times can differ by several hours.
• Check doneness manually: For fruits and vegetables, cut a few pieces in half and look for beads of moisture. For jerky, slice a strip and bend it; it should crack but not break, and no raw-looking interior should remain.
• Jerky and meat safety: Safe jerky depends on reaching a safe internal temperature, starting with high-quality meat, using proper curing or marinating steps, and following validated recipes. Drying time alone is not a guarantee of safety.
• Use a thermometer: An oven or probe thermometer can help confirm both dehydrator air temperature and internal meat temperatures recommended by trusted food safety authorities.
• Storage and shelf life: Allow dried foods to cool, condition them in jars for a few days (shaking daily to check for condensation), and store them in airtight containers away from light. Discard anything that shows mold, off odors, or unusual texture changes.

For authoritative guidance on safe dehydrating and jerky preparation, consult national or regional food safety resources or extension services that publish tested procedures and temperature recommendations.

Quick comparison of typical drying behaviors

Using the calculator effectively

To get the most useful estimates:

• Select the closest matching food type (fruit, vegetable, herb, or meat/jerky).
• Measure or approximate average slice thickness in millimetres; avoid mixing very thin and very thick pieces on the same tray.
• Enter the dehydrator temperature in degrees Celsius. If your dial uses Fahrenheit, convert it or use a separate temperature converter.
• Weigh the batch to get the starting weight in grams so the final weight estimate is meaningful.

Use the output as a guide for when to start checking doneness, not as a promise that food will be ready at an exact hour.