Grass seed sprouts at varying rates. Ryegrass and fescue grass seed are the fastest to germinate. Ryegrass sprouts as soon as five to 10 days, whereas fescue takes one week to 15 days. Bent grass and bermuda grass take from 10 to 15 and 10 to 30 days, respectively. Centipede and buffalo grass germinate in two to four weeks but bluegrass is slower--taking about three to four weeks to start sprouting.
Sow grass seed that has a high germination rate. The best bet is to use a grass seed with a 90 to 95 percent germination rate but some varieties will be closer to 80 percent.
Expect it to take several weeks after the seed first sprouts to grow into a lawn. Your specific growing conditions will play a role in the time line. For best results, keep the soil moist until the lawn fills in completely. Avoid mowing until the grass is two inches high.