Lot Coverage Calculator

How Do You Calculate Lot Coverage?

Divide the footprint of every roofed building on the lot by the lot area, then multiply by 100. That gives you your lot coverage percentage.

To find the most you can build, flip it around: lot area × maximum coverage % = maximum footprint.

1. Find your lot area on your deed, plat map or county assessor record, or multiply width by length.
2. Look up the maximum lot coverage for your zoning district in the local zoning code.
3. Multiply the two. A 6,000 sq ft lot at 40% allows a 2,400 sq ft footprint.

What Does the Lot Coverage Percentage Mean?

It is the maximum share of the lot that structures can sit on. A 35% limit means 65% of the lot has to stay open, whether as yard, driveway or garden.

Cities use it to keep open space, manage stormwater runoff and stop lots from being built edge to edge. Each zoning district sets its own number.

What Size House Can I Build on My Lot?

Start with the lot coverage limit, then check it against your setbacks. The house has to fit inside both. The calculator above uses whichever is smaller.

Multiply that footprint by the number of stories for a rough maximum house size. Then check two more limits: the height limit and the floor area ratio. You can run the second one with our floor area ratio calculator.

If you only know your setbacks, the setback calculator will show the buildable area inside them.

Worked Example: 60 × 100 Lot

That 2,400 sq ft footprint has to hold the house, an attached or detached garage and any covered patio. Going over it usually means a variance or a redesign.

What Is a Good Lot Size to House Size Ratio?

There is no single right ratio. Your zoning sets the ceiling. In the example above, a 6,000 sq ft lot holds a 2,400 sq ft footprint, which is a 40% ratio on the ground.

For total living space, compare floor area to lot area instead. That number is the floor area ratio, and many codes cap it separately.

What Counts Toward Lot Coverage?

Most codes count anything with a roof. That includes the house, garages, carports, covered porches, sheds and accessory dwelling units.

Uncovered decks, patios, driveways and pools are often left out. Some cities count them under a separate impervious surface limit, though, so read the definitions section of your code.

Where Do I Find My Lot Coverage Limit?

It is in your city or county zoning ordinance, usually in a table called development standards, site standards or bulk regulations. First you need your zoning district. Search for your city's zoning map to find it, then look up the code for that district.

Planning a commercial lot? Check parking too with the parking ratio calculator, since required parking often takes up more ground than the building.

Frequently Asked Questions

What is a typical lot coverage limit?

It depends on the zoning district. Many single-family zones allow somewhere between 30% and 50% of the lot to be covered, while denser districts often allow more. The only number that counts is the one in your own zoning code.

Does a driveway count toward lot coverage?

Usually not, because most codes only count roofed structures. Some cities use an impervious surface limit instead, and that one does count driveways, patios and walkways. Check which rule your code uses.

Is lot coverage the same as floor area ratio?

No. Lot coverage limits the footprint on the ground. Floor area ratio limits the total floor area across all stories. A two-story house can meet the coverage limit and still go over the FAR limit.

What if my house is over the lot coverage limit?

A house that was legal when it was built can usually stay as it is. Adding more footprint would normally need a variance from your city or county. Talk to the planning department before you design an addition.