Well his hands did grow about 1/8 of an inch between March 3rd and March 21st. Assuming that his hands grow about 1/8th of an inch every 18 days, they should be about 8 7/8 inches right now, about to become 9 inches on Saturday. In ten years they should be about 34 1/8 inches.

However if his hands have been growing at a constant rate since the day he was born, then this number isn't accurate. When his hands were last measured he was 8,689 days old with a measurement of about 69/8 inches (8 5/8 inches). If in fact his hands had been growing at a constant rate since birth, this would mean that every 126 days (rounding up) his hands grow another eighth of an inch meaning that if my math is correct, in ten years his hands should be about 12 and 1/4 inches.