1 fluid ounce of water was supposed to weigh 1 ounce. But municipal differences have foiled that equivalency over time. The goal with Metric is that this won't

1 fluid ounce of water was supposed to weigh 1 ounce. But municipal differences have foiled that equivalency over time. The goal with Metric is that this won't happen - we'll see how long it takes for one group to claim their meter is 1.1 official meters.