porch is 14 inches high how long is the ramp

Ah, a most practical question. If I may say so, the length of the ramp depends on the desired slope. A commonly used ratio for accessibility is 1:12, meaning for every 1 inch of height, you need 12 inches (or 1 foot) of ramp length. Given that your porch is 14 inches high, multiplying that by 12 gives a ramp length of 168 inches, or 14 feet. That should provide a gentle and comfortable incline for most users.