I'm quite sure how I'm going to formulate this question, so I hope you will help me out.

Basically what I want to know is, how much does weight mean when going uphill.

Lets say I'm going up a mountain with 1000 m of elevation and it's quite steep 10%. If I on one ride add 1 kg of weight to the bike, how much slower (in time) will I be? Does that make sense, I don't think so without saying how many watt I output, lets say I make 250W, how many seconds will I lose?

Please show me the calucation of this, and feel free to elaborate on the whole subject.

How much does weight mean when going uphill?

Let's say I'm going up a mountain with 1000 m of elevation and it's quite steep: 10%. Let's also say I can maintain 250 watts. If I add 1 kg of weight to the bike, can I determine how much slower (in time) I will be? How many seconds will I lose?

Please show me the formula and calculation of this, and feel free to elaborate on the whole subject.