Here's my take at the subject:
Let's say the blockhead is one inch tall.
He's also about 42/3 bricks tall. That makes 42/3 bricks about 1 inch tall.
12 * 42/3 = 56, so 56 bricks stacked on top of each other are about a foot tall.
Each brick is 3 plates tall, and 56 * 3 = 168. So 168 stacked plates are about a foot tall.
168 / 12 = 14, so 14 stacked plates are an inch tall.
In torque units, a 1x1f plate is 0.5 x 0.5 x 0.2.
14 * 0.2 = 2.8, so 2.8 torque units are an inch.
2.8 * 12 = 33.6, so 33.6 torque units are a foot.
In conclusion:
1 inch = 1 blockhead = 42/3 bricks = 14 plates = 2.8 torque units.
1 foot = 12 blockheads = 56 bricks = 168 plates = 33.6 torque units.
However, these measurements only apply to blockland, as the blockhead is around half the size of the default torque player which is probably intended to be around 6 feet tall.