Originally Posted by
penlu
My methodology for guessing power in a steady state: I've thrown my gears and a bunch of cadences into a speed calculator, and the speed numbers into a power calculator. Memorized a bunch of music with known bpm to estimate my cadence while riding. Memorized a few of the table entries. With that I can get a rough wattage by 1. looking at my current gear, 2. figuring out what bpm I'm lining up with, and 3. adjusting for the headwind or tailwind I recall from forecast.
It's a little simpler when climbing a steepish hill because you don't have to worry quite so much about aerodynamic drag -- when climbing a steep hill, there's a rule of thumb that gets you close to the right watts/kg.
For a steep hill, multiply the hill's gradient by your speed in km/h, then by 3. If you measure your speed in mph, multiply by 5 instead of 3.
For example, suppose you're climbing a 10% hill at 11 km/h. 10% * 11 = 1.1, and 1.1 * 3 = 3.3, so you'd need to be producing 3.3 watts/kg. If you measure in mph, 11 km/h is about 6.5 mph, and 10% * 6.5 = 0.65. 0.65 * 5 = 3.25 watts/kg. So the only thing you really have to remember is 3 if you measure in km/h or 5 if you measure in mph.
Of course, sometimes when you're climbing up a steep hill it's hard to do arithmetic, so there's that.