You will need to rent a commercial floor sander to restain hardwood floors. This equipment is typically rented by the hour and the price will range from $10 to $50, depending on where you live. In addition to this cost, you will need to buy several sanding pads for the machine in three grades -- fine, medium and harsh. Sanding machines have at least three pads. Sanding pads range in price from about $3 to $10 a package for each grade.
Wood stain will also need to be purchased. A gallon of stain is typically sufficient for a large room that will require several coats. This will cost $40 to $60. One room require around a half to a full gallon of polyurethane, which runs between $25 and $50. You will also need to purchase paint brushes or stain applicators, as well as tack cloths, sandpaper or sanding blocks, knee pads and a mask. The total for this equipment will come to around $100 to $150.
Instead of renting a floor sander, if you happen to have a belt sander already on hand, you can use this. It will take longer, but it will save you money. Alternatively, ask around town or at your hardware store and see if someone has a machine they would be willing to let you borrow. You can also save money by waiting for wood stain to go on sale, or by finding coupons for your local hardware store.
The cost to professionally refinish a floor is much higher than doing it yourself. According to the website Cost Helper, at the time of publication, a professional company might charge between $850 to $1,125 to refinish a 225-square-foot room. Newer, no-sand flooring companies may charge about half this amount. If the room is small, you can come out on top by having a professional do it, but otherwise, it is definitely more cost-effective to do the work yourself.