How to use this calculator
Browse the checklist of common items and select everything you plan to store in your shed. The list includes lawn equipment like mowers and trimmers, seasonal items like snow blowers, sports gear, bicycles, workbench setups, and general storage. Check off each item that applies to your situation.
As you select items, the calculator adds up the floor space each one requires based on standard dimensions. It then applies a 30% buffer for walking space, access to items in the back, and room to open the door fully. This ensures your shed is functional, not just technically large enough to fit everything.
The result recommends a standard shed size (such as 8x10, 10x12, or 12x16) that fits your needs. It also shows the minimum door width required for your largest item, which is especially important if you need to roll a riding mower or ATV in and out. Use the recommendation as your starting point when shopping for or building your shed.
How to choose the right shed size
The number one mistake people make when buying a shed is going too small. Once you add up everything you want to store, you still need room to walk around, reach items in the back, and open the door fully. This calculator adds 30% walking space on top of your storage footprint.
Think about future needs too. If you might get a snow blower or workbench in a year or two, plan for it now. Going up one size from your minimum is almost always worth it.
Frequently asked questions
What size shed do I need for a riding mower?
A riding mower alone needs about 16 square feet of floor space. But you also need room to maneuver it in and out, plus space for other items. A 10x12 shed (120 sq ft) is the minimum recommended size if you have a riding mower plus basic lawn tools and equipment.
Do I need a permit to build a shed?
Most areas require a building permit for sheds over 120 square feet (10x12). Smaller sheds may not need a permit but still must follow setback rules (distance from property lines). Always check with your local building department before starting.
Wood vs metal vs resin sheds?
Wood sheds look best and can be customized but need regular maintenance (painting and sealing). Metal sheds are affordable and durable but prone to condensation and dents. Resin (plastic) sheds are maintenance free, resist rot and insects, but can look less natural and may not be as sturdy in high winds.
Does a shed need a foundation?
Every shed needs some type of foundation to keep it level and off the ground. Small sheds (under 8x10) can sit on concrete blocks or a gravel pad. Larger sheds should have either a crushed gravel pad with timber frame, concrete slab, or pier blocks. A proper foundation prevents rot, settling, and floor damage.