What the site lets you build
Site area, the floor area ratio and the coverage the zoning allows, and you get the floor area, the footprint and the stories that fit.
Feasibility in two numbers
Most zoning codes control a site with two ratios: how much floor area may be built relative to the site, and how much of the site the building may cover. Together they decide the envelope before a line is drawn.
Definitions vary. Some codes exclude basements, parking, balconies or plant from the floor area; some measure coverage to the eaves and others to the footprint. Read the code for the site and apply the ratios the way it does.
Use the stories figure as a sanity check: a floor area ratio of 1.5 on 40 percent coverage means roughly four stories, which already tells you a great deal about the building.
Other free tools
- Scale ConverterConvert lengths between a scaled drawing and real size at 1:50, 1:100, 1:200 and more, in metric or imperial. Free, no sign up.
- Unit ConverterConvert length, area and volume between metric and imperial units: meters, feet, square meters, square feet, cubic meters, cubic yards and more.
- Stair and Ramp CalculatorWork out risers, riser height, tread depth and total run for a stair, or the length and landings for an accessible ramp, from the total rise.
- Project Cost EstimatorEstimate a construction budget from floor area, building type and level of finish, with design fees and contingency on top. Free, for early conversations.
- Project Timeline EstimatorEstimate a building project timeline phase by phase, from brief and concept to construction and handover, by floor area and complexity.
- Material Quantity EstimatorEstimate concrete volume, brick and block counts, paint litres and tile counts from dimensions, with a waste allowance. Free, no sign up.
- Roof Pitch CalculatorWork out a roof pitch in degrees, as a ratio and as a gradient from rise and run, with the rafter length. Free, no sign up.
- Window to Wall Ratio CalculatorCalculate the window to wall ratio of a facade and check daylight with a glazing to floor area rule of thumb. Free, no sign up.
- Parking CalculatorCalculate parking spaces and parking area for housing, offices, retail and hotels at common ratios, with accessible spaces. Free, no sign up.
- Occupancy CalculatorCalculate occupant load from floor area and use, with the number of exits and total exit width it needs. Free, for a first check of a plan.
- Sun Angle CalculatorCalculate sun altitude and azimuth for a latitude, date and hour, with shadow length, for shading studies and renders with correct light.
- Print Size CheckerCheck whether an image has enough pixels to print at a given size: resolution in dpi, a quality reading, and the largest print at 300 dpi.
- Aspect Ratio PlannerPlan a crop to a target aspect ratio from an image size: the exact pixel dimensions that fit and the pixels lost on each side. Free, no sign up.
- File Size EstimatorEstimate image file size from pixel dimensions and format, JPEG, WebP, PNG or TIFF, and check whether it fits an email. Free, no sign up.
The numbers are done. Now the image.
Turn the sketch, plan or model into a render the client can react to.