Can I use an architect scale ruler on a site plan?

No. Site plans drawn in engineer scale use decimal divisions (10, 20, 30 and so on per inch), not the fractional inch-to-foot scales on an architect ruler. Use the engineer side or calibrate in software.

Why do site plans and floor plans use different scales?

A lot and its grading cover far more ground than a floor plan, so site plans need a smaller scale to fit the sheet, and civil engineers work in feet and decimals rather than feet and inches.

What does 1" = 20' mean on a site plan?

1" = 20' is an engineer scale: one inch on the sheet equals 20 feet on the ground, a ratio of 240 to 1. Engineer scales are used on site, civil and landscape plans. Other common ones are 1" = 10', 30', 40', 50' and 60'.

Formula

Real feet = paper inches x feet per inch

Worked example

A property line that measures 2 in on a 1" = 20' site plan.

1.2 x 20 = 40 ft

The property line is 40 ft long.

Measure it in MetreMate

Use Manual Scale on the site plan: click both ends of a dimensioned line, such as a property line, and type its length. Every measurement after that is in feet.

See the Manual Scaling feature

Related terms

Architect scale (1/4" = 1'-0")
Plan set (sheet index)
Linear foot

Frequently asked questions

Back to the construction takeoff glossary

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