Lighting designs mix metric and imperial units constantly. Photometric files and European products are in meters, while many drawings and mounting heights in North America are in feet. One meter is about 3.281 feet, and one foot is exactly 0.3048 meter, so you can convert in either direction with a single multiplication.

Some everyday examples help to check the result. A ceiling height of 2.4 meters is 8 feet, a 3 meter room dimension is 9.84 feet, and a 10 foot mounting height is 3.05 meters. Throw distances for spotlights and the spacing of fixtures also need consistent units, because the inverse square law makes errors in distance count twice.

Convert all the dimensions at the start of a calculation and then work in one system, which avoids mixing units partway through. Round sensibly, since a design rarely needs more than one or two decimal places, but keep extra precision during the calculation and round only the final result.