Convert feet to inches. Multiply the feet amount by 12 to get inches.
one foot equals 12 inches one inch equals 0.0833333333333 feet
12' 3 1/4"multiply the foot amount by 12 and add the leftover inches;
12 * 12 = 144 + 3 1/4 = 147 1/4
12' 3 1/4" = 147 1/4 inches