Crop Drying Time Calculator & Dry to Safe Moisture
Dries paddy
Plan grain drying — get the water to remove, the dried weight, the drying timeby sun, solar or mechanical dryer, and the heat energy and diesel it takes.
Enter your batch & method
Safe storage moisture for Paddy / Rice: 14%. Removal rate: sun ≈ 0.6, solar ≈ 1.0, mechanical ≈ 0.6 pts/hr.
Next: 14% is safe for storage. Cool the grain before bagging and store dry.
Crop drying — key facts
- Dried weight
- Wi·(1−Mi)/(1−Mf)
- Paddy safe
- ≈ 14%
- Wheat safe
- ≈ 12%
- Sun removal
- ≈ 0.6 pts/hr
- Solar dryer
- ≈ 1.0 pts/hr
- Evaporation heat
- ≈ 2.26 MJ/kg water
- Diesel energy
- ≈ 38.6 MJ/L
- Privacy
- Runs in your browser; nothing uploaded
Dry it right, store it safe
Grain spoils in store if it's too wet — mould, heating and insects all thrive on moisture. Drying down to the safe storage moisture is the single most important post-harvest step, but it costs time, weather windows and (for dryers) fuel. The water you must remove is fixed by physics: dry matter is conserved, so the dried weight and the kilograms of water to evaporate follow directly from your start and target moisture.
This tool gives you that exact mass-balance plus a practical time estimate for sun, solar or mechanical drying, and for heated dryers it adds the heat energy and diesel needed. Use it to decide whether the sun will finish before the next rain, to size a dryer run, or to compare the fuel cost of mechanical drying against the risk of waiting. Then cool the grain and pair with the Grain Moisture Shrinkage and Grain Storage Capacity tools.
Beat the weather
See if sun drying will reach safe moisture before the next rain.
Size a dryer run
Get the run-hours and fuel for a mechanical drying batch.
Know the dried weight
Plan storage and sales on the real post-drying weight.
Compare methods
Weigh free-but-slow sun against fast-but-fuelled mechanical drying.
Frequently Asked Questions
How much water do I remove when drying grain?+
It's a mass-balance: the dry matter stays constant while water leaves. Final weight = wet weight × (1 − initial moisture) ÷ (1 − final moisture), and water removed = wet − dried. For example, 1000 kg of paddy at 24% dried to 14% loses about 116 kg of water and weighs ~884 kg. The tool computes this exactly.
How long does it take to dry grain?+
It depends on the method and conditions. The tool estimates time from a moisture-point removal rate: roughly 0.6 points/hour in open sun, ~1.0 in a solar dryer, and more in a heated mechanical dryer (rising with air temperature). It then converts to sun-days (about 7 effective sun-hours per day) or dryer run-hours.
What is safe storage moisture?+
The moisture level at which grain stores without moulding or insect build-up — about 14% for paddy, 12% for wheat, 13% for maize, 12% for soybean, 9–10% for groundnut and pulses, and lower for spices. The tool defaults the target to each crop's safe moisture and warns if your target is still too wet.
How is mechanical drying energy calculated?+
Removing water needs heat: about 2.26 MJ per kg of water evaporated. Dividing by the dryer's efficiency (default 50%) gives the fuel energy, which the tool also expresses in kWh and litres of diesel (≈38.6 MJ/L). It's an estimate — real dryers vary with design, airflow and ambient conditions.
Why does drying cause weight loss?+
Because you're removing water, which has weight. The 'shrinkage' is purely the water lost — the valuable dry matter (starch, protein, oil) is conserved. This is why grain is traded on a moisture basis: buyers adjust for the water you'd otherwise be selling as grain.
Sun, solar dryer or mechanical — which is best?+
Sun drying is free but slow, weather-dependent and risks contamination and over-drying. Solar dryers are faster and cleaner. Mechanical dryers are fastest and weather-proof but cost fuel. The tool lets you compare the time (and energy for mechanical) so you can choose for your batch and season.
Can I dry too fast or too much?+
Yes. Drying grain too fast or too hot causes cracking (especially in paddy, lowering milling quality), and over-drying below the safe moisture wastes energy and loses sellable weight. Aim for the safe storage moisture at a moderate temperature, and rest/temper the grain between passes in mechanical drying.
Does this work for spices and other produce?+
The mass-balance for water removed is valid for any crop. The time estimate is tuned for grains and seeds; very high-moisture produce (like fresh chilli or turmeric going from 70–80% down) will take longer in reality and usually needs repeated sun-days or a dryer. Use the water-removed figure as the firm number.
How do I measure grain moisture?+
Use a grain moisture meter for a quick, reliable reading, or the oven method (weigh, dry at 130 °C, re-weigh) for accuracy. Measure at several points in the lot, as moisture varies. Enter your starting moisture and the safe target, and the tool does the rest.
Why cool grain after drying?+
Hot grain straight from a dryer will sweat and re-absorb moisture when bagged, encouraging mould. Let it cool to near ambient before storage. The tool tells you the dried weight and safe moisture; always cool and store in a dry, ventilated, pest-proof structure.