Grain Drying Calculator
Calculate grain moisture water shrink %, net dry bushels delivered, water weight evaporated, propane LP fuel gallons required, and fuel drying costs ($/bu).
Calculate Grain Moisture Shrink & Propane Drying Cost
Enter wet grain volume (bushels), initial harvest moisture %, target dry storage moisture %, handling shrink %, and LP propane price.
Calculation Results
Calculated using official USDA grain moisture shrink equations: \text{Water Shrink \%} = \left[ \frac{\text{Wet \%} - \text{Target \%}}{100 - \text{Target \%}} \right] \times 100
Quick Summary
The Grain Drying Calculator evaluates water shrink loss ($\text{Water Shrink \%} = \frac{\text{Wet \%} - \text{Target \%}}{100 - \text{Target \%}} \times 100$), net dry bushels delivered, gallons of water evaporated, propane LP fuel usage, and drying cost per bushel ($/bu).
Formula Explanation
\text{Water Shrink \%} = \left[ \frac{\text{Initial Moisture \%} - \text{Target Moisture \%}}{100 - \text{Target Moisture \%}} \right] \times 100
\text{Net Dry Bushels Delivered} = \text{Wet Bushels} \times \left(1 - \frac{\text{Water Shrink \%} + \text{Handling Loss \%}}{100}\right)
\text{Propane LP Fuel (gallons)} = \text{Wet Bushels} \times (\text{Initial \%} - \text{Target \%}) \times 0.020 \text{ gal/bu/\%}How It Works
Harvesting high-moisture grain prevents field shattering and weather losses, but requires artificial drying for safe bin storage. The Grain Drying Calculator applies USDA moisture shrink equations and propane fuel consumption rates, calculating net dry bushels delivered and fuel cost per bushel.
Step-by-Step Worked Example
Practical Problem: A farmer harvests 10,000 bushels of corn at 22% moisture and dries it down to 15% target moisture (7% points removed) plus 0.5% handling shrink. Propane LP gas costs $1.60/gallon. Calculate water shrink %, dry bushels delivered, propane fuel required, and total drying cost.
- Step 1: Calculate water shrink percentage: $[(22 - 15) / (100 - 15)] \times 100 = (7 / 85) \times 100 = \mathbf{8.235\%\text{ water shrink}}$.
- Step 2: Add handling shrink (0.5%): $8.235\% + 0.5\% = \mathbf{8.735\%\text{ total shrink}}$.
- Step 3: Calculate net dry bushels delivered: $10,000 \times (1 - 0.08735) = \mathbf{9,126.5\text{ dry bushels}}$.
- Step 4: Calculate water weight removed: $(10,000 \times 56) - (9,126.5 \times 56) = 560,000 - 511,084 = \mathbf{48,916\text{ lbs water}}$ ($5,865\text{ gallons water}$).
- Step 5: Calculate propane fuel gallons & cost ($1.60/gal): $10,000\text{ bu} \times 7\%\text{ points} \times 0.02 = \mathbf{1,400\text{ gal LP}}$; $1,400 \times \$1.60 = \mathbf{\$2,240.00\text{ total drying cost}}$ ($\$0.224/\text{bu}$).
Real-World Calculation Examples
Scenario 1: 10,000 Bu Corn (22% to 15% Moisture)
Parameters: 10,000 bu, 22% wet, 15% target, $1.60 LP
Result: 9,127 dry bushels (8.24% water shrink, 1,400 gal LP, $0.224/bu drying cost).
Scenario 2: Wet Harvest Corn (26% to 15% Moisture)
Parameters: 10,000 bu, 26% wet, 15% target
Result: 8,653 dry bushels (12.94% water shrink, 2,200 gal LP fuel needed!).
Scenario 3: Soybean Drying (17% to 13% Moisture)
Parameters: 5,000 bu soybeans, 17% wet, 13% target
Result: 4,745 dry bushels (4.60% water shrink loss).
Scenario 4: High Density Commercial Grain Elevator (1.4% Fixed Shrink)
Parameters: 10,000 bu, 22% wet, elevator 1.4% shrink factor
Result: 9,020 dry bushels (Commercial elevator shrink table calculation).
Key Benefits of Using This Calculator
Official USDA Water Shrink Formula
Applies exact USDA moisture shrink equations rather than loose thumb rules.
Water Weight Evaporated Output
Calculates exact pounds and gallons of water evaporated during high-temp grain drying.
Propane LP Fuel Expense ($/bu)
Computes propane LP gas gallons and per-bushel drying cost ($/bu) to evaluate on-farm drying vs commercial elevator discounts.
100% Free & Client-Side
Executes locally in your browser with zero latency or web server transmission.
Frequently Asked Questions (FAQ)
What is official USDA water shrink formula for grain?
The USDA water shrink formula is $\text{Water Shrink \%} = \left[ \frac{\text{Initial Moisture \%} - \text{Target Moisture \%}}{100 - \text{Target Moisture \%}} \right] \times 100$.
Why is water shrink % higher than simple moisture point subtraction?
Drying 22% corn to 15% removes 7 points of water, but water shrink is 8.24% because removing water decreases the total remaining weight denominator ($7 / 85 = 8.24\%$).
What safe moisture levels are required for long-term grain bin storage?
Safe storage moisture levels: Corn = 14% to 15% (6–12 months); Soybeans = 13%; Wheat = 13%.
How much propane LP gas does a high-temperature grain dryer use?
High-temperature continuous cross-flow dryers consume 0.018 to 0.022 gallons of propane LP fuel per bushel for every 1% of moisture removed.
What is in-bin natural air drying (low temperature drying)?
Natural air drying uses unheated ambient air blown through a full perforated bin floor at 1.0 to 2.0 CFM/bu to dry corn under 20% moisture during cool autumn weather.
What is combination drying (high-temp + in-bin aeration)?
Combination drying uses a high-temp dryer to remove moisture down to 18%, transferring hot corn into a bin to finish drying to 15% via natural air cooling, saving 30% to 40% fuel!
What is stress cracking and BCFM in dried corn?
Rapid cooling of hot corn (>180°F) causes stress cracks in endosperm starch, increasing Broken Corn and Foreign Material (BCFM) fines during handling.
What is commercial elevator drying charge vs shrink discount?
Elevators charge a drying fee (e.g. $0.04 per point of moisture per bushel) PLUS a moisture shrink discount (e.g. 1.4% shrink per point).
How many BTU of energy are needed to evaporate 1 lb of water from grain?
High-temperature dryers require 2,000 to 2,500 BTU of heat energy per pound of water evaporated from wet grain.
How do I convert gallons of LP propane to BTU?
1 gallon of liquid propane (LP) contains approximately 91,500 BTU of heat energy.