🚜 Gravity Wagon Calculator
Calculate volume and capacity of gravity wagons, grain boxes, and hopper trailers
Enter Wagon Dimensions
Cross-section view • L=length, Wt=top, Wb=bottom
📊 Gravity Wagon Results
Length (L)
12 ft
Top Width
6 ft
Bottom Width
1.5 ft
Total Height
5.5 ft
Volume (ft³)
283 ft³
Volume (bu)
227 bu
Top Section
216 ft³
Hopper Section
67.5 ft³
📝 Step-by-Step Solution
Given: L = 12 ft, Wt = 6 ft, Wb = 1.5 ft, Ht = 3 ft, Hh = 2.5 ft
Top section (rectangular prism): V_top = L × Wt × Ht = 12 × 6 × 3 =
216 ft³
Hopper section (trapezoidal prism): V_hop = L × ((Wt + Wb)/2) × Hh =
12 × 3.75 × 2.5 = 112.5 ft³
Total volume = 216 + 112.5 = 328.5 ft³
Volume in bushels = 328.5 ÷ 1.244 = 264.1 bushels
📐 Gravity Wagon Formulas
Top Section: Vtop = L × Wt × Ht
Hopper Section: Vhop = L × ((Wt + Wb) / 2) × Hh
Total: V = Vtop + Vhop
Bushels: V_bu = V_ft³ ÷ 1.244
Understanding Gravity Wagons
🚜 What is a Gravity Wagon?
Farm equipment for transporting grain. Features a V-shaped hopper bottom for gravity unloading through a gate.
📦 Two-Part Shape
Top = rectangular prism. Bottom = trapezoidal prism (V-hopper). Calculate each separately and add.
📏 Key Dimensions
L = length, Wt = top width, Wb = bottom width, Ht = top height, Hh = hopper height.
🌾 Bushel Capacity
1 bushel = 1.244 ft³. Gravity wagons typically 150-500 bushels. Divide ft³ by 1.244.
Frequently Asked Questions
What is the formula for gravity wagon volume?
V = L×Wt×Ht + L×((Wt+Wb)/2)×Hh. Top rectangular section plus
bottom trapezoidal hopper section.
How do I convert cubic feet to bushels?
Divide by 1.244. 1 US bushel = 1.244 cubic feet. Example: 300 ft³
÷ 1.244 = 241 bushels.
What is the hopper section?
The V-shaped bottom. Slopes from top width to narrower bottom
width. Allows gravity unloading through gate.
How do I measure wagon dimensions?
Inside measurements. Length = front to back. Top width = side to
side at rim. Bottom width = at hopper opening.
What if my wagon has a flat bottom?
Set Hh = 0 or Wb = Wt. Calculator handles flat-bottom boxes. Just
use the top section formula.
What is a typical gravity wagon size?
150-500 bushels. Small wagons ~150 bu, standard ~250 bu, large
~400+ bu. Depends on farm needs.
How accurate is this calculator?
Very accurate for standard shapes. Real wagons may have rounded
corners or irregular shapes reducing actual capacity.
What is struck vs heaped capacity?
Struck = level full. Heaped = piled above rim. This calculator
gives struck capacity. Heaped adds 5-10%.
Can I use this for hopper trailers?
Yes, same geometry. Semi hopper trailers, grain carts, and gravity
boxes use similar shapes.
How do I find length from volume?
L = V / cross-section area. Where area = Wt×Ht + ((Wt+Wb)/2)×Hh.
Our calculator solves this.
What units should I use?
Consistent units. All dimensions in feet, inches, or meters.
Calculator converts automatically.
How does grain test weight affect capacity?
Doesn't affect volume. Test weight affects weight per bushel.
Volume capacity stays same regardless.
What if sides are sloped all the way up?
Set Ht = 0. The entire wagon becomes one trapezoidal prism. Hopper
section only.
How do I calculate weight capacity?
Bushels × test weight. Corn: bu × 56 lb. Wheat/Soybeans: bu × 60
lb. Check wagon weight rating.
What is a gravity box vs gravity wagon?
Same thing. "Gravity box" and "gravity wagon" are interchangeable
terms. Both use gravity unloading.
Can I use this for V-bottom containers?
Yes. Any container with rectangular top and trapezoidal V-bottom.
Dumpsters, bins, feeders, etc.
How do I measure hopper height?
From bottom of top section to hopper opening. The sloped portion
of the V-bottom. Not the total depth.