A handheld device for golfers is disclosed which determines the slope from a golf ball's location on the golf course to the cup or pin on a green. The device includes: a housing; a sight mounted on the housing for aiming the device at the flag of the pin; a tilt sensor for measuring the slope or tilt of the aimed device; a display wheel cooperating with the tilt sensor for indicating the slope or tilt of the aimed device; and, a chart affixed to the housing including actual ball to cup distances, slope indications and yardage adjustments which are added to or subtracted from the actual distances to enable the golfer to estimate the effective shot distance of the ball to the cup. A software application is also disclosed for estimating the effective shot distance of a golf ball to a target on a handheld device such as a smart phone.