What size storage unit do I need?
Start with the biggest things you're storing and how much of a home you're emptying. A 10x20 (200 sq ft) is about the footprint of a one-car garage and fits the contents of a multi-room home or most cars; a 10x30 (300 sq ft) is about a large one-and-a-half to two-car garage and holds a large home or a boat on its trailer; a 10x40 (400 sq ft) fits a full home or vehicles plus gear.
Step by step
List the big items first
Furniture, appliances, mattresses, a car, a boat or a trailer decide the size - boxes fill in around them.
Match the floor area
A 10x20 is 200 square feet, about the footprint of a classic one-car garage; a 10x30 is 300 square feet, about a large one-and-a-half to two-car garage, though deeper and narrower [1].
Think in rooms
A 10x20 can comfortably store the contents of a three-bedroom home, and a 10x30 the furniture and belongings of a four-plus-bedroom house when packed well [1]. Room counts are rough - how you pack matters.
Check vehicles and boats
Almost any car fits in a 10x20, but two cars won't. A 10x30 can hold two cars end to end, and boats and RVs are commonly stored in units that size or larger [1].
Use the height
Most of our units have 8- to 10-foot ceilings, so shelving and stacked boxes let a smaller unit hold more.
Leave a walkway
Plan a path down the middle so you can reach things without unpacking everything [2]. If it's tight, go one size up.
Our sizes at a glance
| Unit | Floor area | About the size of | Good for | Monthly rate |
|---|---|---|---|---|
| 10x20 | 200 sq ft | the size of a one-car garage | The contents of a multi-room home or apartment, a car, tools and trade equipment, seasonal gear | Call for today's rate |
| 10x30 | 300 sq ft | a large one-and-a-half to two-car garage | The contents of a large home, appliances, motorcycles, a small boat or trailer, business inventory | Call for today's rate |
| 10x40 | 400 sq ft | a large two-car garage | A full home, long-term moves, vehicles and trailers, boats, ATVs and snowmobiles, bulk business storage | Call for today's rate |
Still not sure? Tell us what you're storing on the reservation form and we'll help you pick.
Sources
- StorageCafe - Large storage units explained: how to know what size you need (July 2, 2026) - 10x20 = one-car garage footprint, three-bedroom home, almost any car; 10x30 = two-car garage footprint, four-plus bedrooms, two cars, boats and RVs
- U-Haul Moving Insider - How to pack a self storage unit (Jan. 24, 2013) - leave a walkway through the middle of the unit
Sources accessed October 19, 2026. Follow your owner's manual for your own vehicle, boat or equipment.
At Sparks Self Storage: 75 drive-up 10x20, 10x30 and 10x40 units on Highway 27 in Prairie du Chien, month-to-month, free disc lock with every new rental. See the units.
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35068 WI-27
Prairie du Chien, WI 53821