OG problem

I've been extract brewing for about 20 batches. When I apply my receipes to the following formula my origional gravities always end up much lower than my estimate. What can I do to raise my OG's? What am I doing wrong during the brewing that might cause my OG's to be so low. Should I boil longer-shorter...add 1/2 my DME late in the boil, etc.

OG in points = (Points) * (lbs of malt used) / (gallons of beer brewed)
for each ingredient that adds to the density of the wort. For malt extracts, "Points" = 35 for syrup (in practice it's about 30) and 42 for dried extract. For speciality grain contributions, Pale Malts = 29 points, vienna/munich/amber = 25, wheat = 26, cara pils = 20, crystal = 8, black = 2.

My most recent brew was a simple IPA with 7 lbs. DME and a pound of seeped crystal grain....according to the formula I should have an OG of about 60 but ended up with 48...I've typically been getting low 40's with 7 or 8 lbs of DME. Thanks.

What temp are you reading you hydrometer at? You may just need to adjust your readings for temperature, and will find that your OG's are much closer to the estimate.

If the error is consistent, there has to something wrong with your hydrometer or the marks on your fermenter. As an example, if you think you have 5 gallons and it is really 6, your hydrometer reading would be spot on.

Changing the timing of the extract adds will not change the gravity.

Finally, if you are steeping, the point values are lower.

Like david_42 said, your hydrometer could be off. Try putting just water in the hydrometer sleeve and see if your reading comes out to 1.000. If it doesn't, your hydrometer is off.