Dehydration Time Calculator Formula

Understand the math behind the dehydration time calculator. Each variable explained with a worked example.

Use the Dehydration Time Calculator

Formulas Used

Base Drying Time

base_hours = food_type

Estimated Drying Time

adjusted_hours = round(food_type * (thickness / 5) * (135 / temp) * humidity)

Minimum (check at)

min_hours = round(food_type * (thickness / 5) * (135 / temp) * humidity * 0.7)

Maximum

max_hours = round(food_type * (thickness / 5) * (135 / temp) * humidity * 1.3)

Variables

VariableDescriptionDefault
food_typeFood Category8
thicknessSlice Thickness(mm)5
tempDehydrator Temperature(°F)135
humidityAmbient Humidity1

How It Works

How to Estimate Dehydration Time

Formula

Time = Base Hours x (Thickness / 5 mm) x (135 / Temp) x Humidity Factor

Thicker slices take proportionally longer. Higher temperatures speed drying. High humidity slows the process because the air can absorb less moisture.

Recommended Temperatures

  • Herbs: 95-110°F (preserve volatile oils)
  • Fruits: 125-135°F
  • Vegetables: 125-140°F
  • Jerky/Meat: 155-165°F (must reach 160°F internal for food safety)

    • Doneness Tests

    Fruits should be pliable but not sticky. Vegetables should be brittle. Jerky should bend and crack but not snap.

    Worked Example

    Apple slices 5 mm thick at 135°F with moderate humidity.

    food_type = 8thickness = 5temp = 135humidity = 1
    1. 01Base time for fruit = 8 hours
    2. 02Thickness factor = 5/5 = 1
    3. 03Temperature factor = 135/135 = 1
    4. 04Humidity factor = 1
    5. 05Estimated = 8 x 1 x 1 x 1 = 8 hours
    6. 06Check at 6 hours, may take up to 10 hours.

    Frequently Asked Questions

    How do I know when food is fully dehydrated?

    Fruits should be leathery and pliable with no moisture when torn. Vegetables should snap or crumble. Jerky should crack when bent but not break in half. Allow pieces to cool before testing, as warm food feels softer than it actually is.

    Can I dehydrate food in my oven?

    Yes, if your oven goes as low as 170°F. Prop the door open slightly for air circulation. Use a thermometer to verify the temperature. Oven drying is less efficient than a dehydrator and uses more energy.

    How should I store dehydrated food?

    Store in airtight containers (mason jars, vacuum-sealed bags, or mylar bags with oxygen absorbers) in a cool, dark place. Properly dried food keeps 6-12 months at room temperature and longer if vacuum sealed.

    Ready to run the numbers?

    Open Dehydration Time Calculator