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Newton Drying Time Calculator

Estimate drying time from a fitted Newton model using initial, target and equilibrium moisture. Convert wet-basis inputs and retain the model’s conditions.

Use this result well

Inputs that matter
Initial moisture, Target moisture, Equilibrium moisture, Fitted drying constant k
Output to expect
Modeled total drying time
  • Check the units and required inputs before comparing results.
  • Keep the assumptions with a copied result so you can reproduce the calculation later.
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Reference & details

How it works

Use the Newton moisture-ratio equation

The model expresses moisture ratio as exp(−kt), where moisture is on the dry basis and equilibrium moisture is subtracted. Solving for time gives −ln(MR)/k.

MR = (Xtarget − Xe) / (Xinitial − Xe); t = −ln(MR)/k

Source: Primary drying research: model equation and dry-basis definitions

Convert the supplied moisture basis

The form accepts wet-basis percent w. Dry-basis water-to-solids ratio is w/(100−w). Using wet percentages directly in MR would produce a different answer.

X = w / (100 − w)

Keep the fitted domain

Use k in inverse hours from a fit under the same material, thickness, temperature, humidity and airflow. Targets must lie above equilibrium and at or below starting moisture. The model does not choose a food-readiness endpoint.

Updated: September 2026

Example Scenarios

Enter 80% initial, 20% target, 5% equilibrium moisture, and k 0.5 per hour.

→ MR is 0.05 and modeled total time is about 5.991465 hours.

Use the same moisture values with k 1 per hour.

→ Modeled time halves to about 2.995732 hours.

Enter 80% initial, 5% target and 5% equilibrium moisture.

→ No finite time is returned: the exponential only approaches equilibrium.

Common Mistakes to Avoid

Scaling drying time directly by a Fahrenheit reading

Use a fitted k for the actual conditions; an absolute Fahrenheit ratio is not a drying-rate model.

Treating modeled target moisture as safe dried food

Follow the food-specific preparation and actual endpoint checks. Moisture arithmetic does not establish water activity or microbial safety.

FAQ

The Newton moisture ratio uses water relative to dry solids. Using the wet-basis percentages directly changes that ratio and the resulting time.

Use a Newton-model fit to measured drying data under the applicable material, slice thickness, airflow, humidity and temperature conditions. A fit from a different setup may not apply.

The exponential approaches equilibrium asymptotically. Reaching equilibrium exactly requires infinite time; targets below it cannot be reached by this model.

No. Use the actual food-specific preparation and endpoint checks. A mathematical moisture target does not validate drying, cooking or storage safety.

It is total model time from the entered initial condition. This form does not track a running dehydrator or changing conditions.

About Newton Drying Time Calculator

Solve the Newton thin-layer drying equation for time to a supplied moisture target. The fitted constant and equilibrium moisture belong to the material and drying conditions being modeled.