A colleague from a previous job once told me: "when a developer gives you an estimate, always double and add one of that unit" (estimate = 2n+1). He told me thi

A colleague from a previous job once told me: "when a developer gives you an estimate, always double and add one of that unit" (estimate = 2n+1). He told me this after a while, because he would often nag me to clarify if I meant 7h or 1 day. i.e. if you estimate 7h, then calculate 2x7+1 = 15h. If you estimate 1d, then calculate 2x1+1 = 3d = 21h. It's a silly joke, but it also gives insight about how we perceive time and the elasticity of estimates. And of course, instead of multiplying by 2, you multiply by a time factor that depends on the risk factors involved (which are also guesstimates, but for me 'x2' would mean a rather low risk factor).