One furlong equals 660 feet
An average time for a furlong is 12 seconds. A really good fast furlong will be between 11 and 12 seconds - known in the parlance as "11 and some change." A very fast furlong is 11 seconds.
A work can be at any distance, though the farther a horse goes, the more you have to save him. You don't say that it's a slow work because he doesn't go every furlong of eight in 11 seconds apiece. You can't expect a certain number of furlongs at really top speed, a certain number at an easy speed to give the horse a breather, and you hope he has enough left in him so that his last furlong will be a good fast one. Some of ther paces are: Blowout (called "Piping Out" in England): This is a sharp fast workout over a short distance. The longest blowout is about a half a mile; usually it's 1/4 or 3/8 of a mile. This is where you get your 11 second furlong - one or two of them - if the horse is a really good runner.
Breeze: This is between a fast gallop and letting the horse really run. An average of 13 seconds a furlong is about right.
Slow breeze: Usually something called a "two-mile lick," that is, a pace at which the horse would run a mile in two minutes. This is an average of 15 seconds a furlong. Also known as a "fast gallop."
Slow gallop: Roughly equivalent to a canter (which is a show-horse term never used by racetrack people). Racehorses have many slow gallops to build up thier stamina and work off their fat. Before a horse gets to gallop, though, trainers like to jog them quite long distances, since this is very beneficial for them.
1/8 one-eighth
2/8 quarter-mile
3/8 three-eighths
4/8 half-mile
5/8 five-eighths
6/8 three-quarters
7/8 seven-eighths
8/8 one-mile