Linear feet (often called Lineal feet) are the same as regular feet. No conversion is necessary. If something is 6 linear feet tall, it is 6 feet tall.

It should be noted, that the correct term is Linear, since Lineal refers to a line of ancestry, not to length.

There are times when the term Linear is used, and times when it is not. I'll give some examples of them.

First a definition. Linear means "a straight line" so a straight line from point A to point B is the linear distance.

One example would be... It is 2200 linear miles from Seattle to Washington DC. But if you were to drive from Seattle to Washington DC, you would have to drive 2700 miles. The linear distance is a straight line from point A to point B, and Freeways rarely are straight.

Another good example would be boards, wire fencing, and rolls of cloth, all of which are often sold in linear feet. That just means they are not taking the width into account. If you bought 100 linear feet of lumber, laying them down end to end would stretch for 100 feet, it wouldn't matter how wide the boards were. If you were to multiply the width of the board, or the width of the roll of cloth, times the linear length, you would get the area.

The same applies for linear yards, linear meters, etc.