If you are not terribly picky, a carpet remnant store is your best bet. It typically costs only about $150 or so to carpet a room up to about 12' by 16' or so. You still need a pad and generally need...
Measure the area of the space to be covered. Multiply by the cost of the unit area of the carpet. A typical economy carpet at Lowe's is about $2.25 per square foot including pad, plus $97 for...
The cost of carpet depends on the area being covered (in square yards in the USA or square meters in the rest of the world) and the relative quality of the carpet material. A rather icky cheap carpet...