[aelzeiny]

I really like this engineer's method of software estimation. It's really close to what Civil Engineers use to estimate load, called Load-Factor-Resistant-Design. That's a fancy way of saying, that we come up with an estimate, then multiply by an uncertainty constant called "Factor of Safety".

Steel in tension, low uncertainty, LRFD safety factor is 1.75. Steel in compression, medium uncertainty, safety factor is 2.5. Anything to do with soil, high uncertainty, safety factor of 4.

Same principal really. If it works for life/death scenarios, it'll work for you!