What Size Transfer Tank Do I Need?
Picking the right size transfer tank comes down to a few practical questions — how much fuel do you actually need to carry, what's already in your truck bed, and which tank shape fits your setup. Get those three things right and the decision becomes pretty straightforward.
Here's what to think through before you buy.
How much fuel do you actually need?
Start with your equipment. Think about everything you typically need to fuel in a single run and add it up. A diesel tractor might take 50 to 80 gallons to fill. A skid steer might take 20 to 30. A generator running all day might burn through 10 to 15. If you're making multiple stops on a single trip, those numbers add up fast.
As a general rule:
- 30 to 50 gallons — a good fit for lighter use. Topping off a single piece of equipment, fueling mowers and small machines, or keeping a generator running. Popular with landscapers and hobby farmers who don't need to move large volumes at once.
- 50 to 75 gallons — the sweet spot for most small farms, contractors, and ranchers. Enough capacity to fully fuel one large piece of equipment or handle two to three smaller machines in a single run.
- 100 gallons and up — for dedicated service trucks, large farming operations, and anyone running high volumes on a regular basis. At this range you're essentially bringing a fuel station with you.
For reference, diesel weighs approximately 7.1 lbs per gallon and gasoline weighs approximately 6.1 lbs per gallon. A full 100 gallon diesel tank adds roughly 710 lbs to your truck. For most three-quarter ton and one-ton trucks that's well within payload capacity, but it's worth knowing the math. On very large tanks — think 200 gallon — payload does become a real consideration.
What's already in your bed?
This is where a lot of buyers get tripped up. It's not just about how long your bed is — it's about what's already occupying that space.
If you're running a gooseneck ball, a fifth wheel hitch, or fifth wheel hitch rails, those take up meaningful real estate in your bed and will affect which tank size and shape will actually fit. Measure your usable space with that equipment in place, not just the raw bed dimensions. Every tank on our site includes a full diagram with dimensions on the product page — use those numbers against your actual available space before you order.
Short bed trucks require extra attention here. The cab-to-tailgate distance is shorter to begin with, and once you account for a gooseneck or fifth wheel setup the usable space shrinks further. The good news is there are tank shapes specifically designed for tighter beds.
Which shape fits your setup?
Transfer tanks come in several shapes and each one solves a different fitment problem.
Rectangle is the most common configuration and fits straightforwardly in most truck beds. If you have a clean open bed without a toolbox or hitch equipment in the way, a rectangle tank is usually the simplest choice.
L-shape tanks are designed for trucks that already have a toolbox. The lower portion of the tank slides underneath the toolbox, letting you run both without sacrificing one for the other. If you're not giving up your toolbox, this is the shape to look at.
Taller tanks are narrower from the cab to the tailgate but taller in height. They take up less front-to-back bed space, which makes them a practical option when you're working with limited cab-to-tailgate room but have vertical clearance to spare.
Wedge style tanks are popular with farmers and anyone running a gooseneck trailer. The angled shape of the tank means you can still see over it to your gooseneck ball or trailer connection — a small thing until you're trying to hook up a trailer and your tank is blocking your sightline.
Tank and toolbox combos are exactly what they sound like — a single combined unit that gives you a transfer tank on the bottom and a lockable toolbox on top. These are a clean solution if you want both without the fitment puzzle of matching separate components. At Midway Tanks we carry combo units from 30 gallons up to 111 gallons.
A note on bed covers
If you're running a tonneau cover or bed cover, make sure the tank you choose is designed to fit underneath it. Tank height alone isn't the whole story — the fill port on top of the tank typically adds an additional 2 to 2.5 inches above the tank lid. That extra height needs to clear your cover when it's closed. Every product page includes a dimension diagram so you can check the full height including the fill port before you order.
What size do we carry?
At Midway Tanks we carry gasoline approved transfer tanks from 30 to 110 gallons and diesel tanks up to 200 gallons, across all the shapes listed above. All tanks come with mounting tabs and some include full mounting hardware — check the individual product listing for details.
If you're not sure which size or shape works for your specific truck and setup, give us a call. Knowing your bed dimensions, what equipment is already in the bed, and what you're planning to fuel is usually enough to point you in the right direction quickly.