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MyFloorPlanMaker

Ground Coverage Calculator

List the parts of your building that stand on the ground and enter your plot. The ground coverage calculator adds up the footprint, divides it by the plot and compares it with the coverage figure from your rules, then shows the open area left.

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Ground coverage calculator

Planning aid, not a compliance check; FAR/FSI, coverage and setbacks are set by your local development rules. Not checked: setbacks (see the setback calculator), permeable-area or green-cover rules.

Start from:

Bare numbers are meters; 190 mm works too.

 

Parts of the building on the ground (outer faces)

 

 

 

Porches, carports and sheds: your rules decide.

Assumptions

Change any value to match your product or local rules.

 

Basis: Example only: replace it with the figure from your local development rules.

Ground coverage
54.00%
Footprint that counts
270.00 m²
2,906.3 sq ft
Largest footprint at your figure
300.00 m²
3,229.2 sq ft
Against your coverage figure
Within the figure you entered, 30.00 m² (322.9 sq ft) to spare
Open area left on the plot
230.00 m²
2,475.7 sq ft

The parts that count cover 54% of the plot (270.00 m² (2,906.3 sq ft)); at the 60% you entered the footprint can be up to 300.00 m² (3,229.2 sq ft).

Counted

  • House: 15.00 m × 18.00 m = 270.00 m² (2,906.3 sq ft)
20.00 m25.00 mHouse
How this was calculated
  • Footprint = sum of width × length of the parts that count
  • Ground coverage = footprint ÷ plot area × 100
  • Largest footprint = plot area × your coverage figure ÷ 100
  • Open area = plot area − every part (counted or not)
  1. Plot area = 20.00 m × 25.00 m = 500.00 m²
  2. Footprint that counts = 15.00 m × 18.00 m = 270.00 m²
  3. Ground coverage = 270.00 m² ÷ 500.00 m² × 100 = 54%
  4. Largest footprint = 500.00 m² × 60% = 300.00 m²
  5. Open area = 500.00 m² − 270.00 m² = 230.00 m²

How it works

  1. Enter the plot

    As width × depth for a rectangle, or as an area for any shape.

  2. List the parts

    House, garage, covered porch, shed: each one’s width and length, measured to the outer wall faces. Mark whether your rules count it.

  3. Enter your coverage figure

    The maximum share of the plot your rules let a building cover. The default is an example only.

  4. Read the result

    Coverage = counted footprint ÷ plot × 100. You also see the largest footprint at your figure, what is spare or over, and the open area.

Worked example

A 500 m² plot with a 15 × 18 m house: the footprint is 270 m², and 270 ÷ 500 × 100 = 54% coverage. At a 60% coverage figure the footprint can be up to 300 m², leaving 30 m² (about 322.9 sq ft) to spare.

In feet: a 40 × 60 ft plot is 2,400 sq ft. A 30 × 45 ft house (1,350 sq ft) plus an 8 × 12 ft covered porch (96 sq ft) makes 1,446 sq ft, which is 60.25% of the plot (134.33779584 m²). Against a 60% figure that is 6 sq ft over. If your rules leave the porch out, coverage drops to 56.25%.

Coverage and FAR

Ground coverage looks at one level: the share of the plot the building stands on. FAR adds up the floor area of every floor. A three-floor house with a 150 m² footprint on a 500 m² plot covers 30% of the plot and has an FAR of 0.9. Rules often set both, and you need to meet each one.

Lot size to house size ratio

The lot size to house size ratio is usually the coverage ratio: house footprint ÷ lot area × 100. A 30 × 40 ft house (a 1,200 sq ft footprint) on a 30 × 50 ft lot (1,500 sq ft) gives 1,200 ÷ 1,500 × 100 = 80%. Enter the lot as the plot and the house as one part, and the calculator works it out.

If you mean the floor area of the whole house against the lot, that is the floor area ratio (FAR) instead. A two-storey house with 2,400 sq ft of floor area on the same 1,500 sq ft lot has an FAR of 2,400 ÷ 1,500 = 1.6; the FAR calculator does that sum. If you only have the lot’s side lengths, the plot area calculator gives its area first.

What counts as footprint

Rules differ on porches, carports, sheds, balconies above the ground floor, eaves and sunshades. Some count anything with a roof; others count only enclosed space. List every part, mark what your rules count, and the parts you mark as not counted still come off the open area.

Measuring a footprint

Measure each part to the outside faces of its walls, not the rooms inside. Your rules may say whether to measure to the wall or to the roof edge where the roof overhangs. For an odd-shaped building, split it into rectangles and enter each one as a part.

Frequently asked questions

How is ground coverage calculated?

Add up the footprint of the parts that count, divide by the plot area and multiply by 100. A 270 m² house on a 500 m² plot covers 54%.

What is the difference between ground coverage and FAR?

Coverage measures the footprint on the ground as a share of the plot. FAR measures the floor area of all floors against the plot. A taller building raises FAR without changing coverage.

Do porches and carports count?

Your local rules decide. Some count every roofed part, others only enclosed rooms. Add each part as its own row and mark it counted or not.

Is coverage measured to the walls or the roof edge?

Your rules decide that too: they say whether to measure to the walls or the roof edge. Measure the way your rules describe.

How do I find the maximum footprint for my plot?

Multiply the plot area by your coverage figure and divide by 100. A 500 m² plot at 60% gives 300 m². Setbacks can leave a smaller area; check them with the setback calculator.

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