Also, many metronomes have a "tap" feature where you tap the beat and it tells you the bpm.
Instead of using seconds, which are a pretty abstract reference point, you might try figuring out the tempos of some real familiar recorded songs. You've heard Back in Black, Another One Bites the Dust, Magic Man, or whatever a thousand times- you should be able to pull up their tempos from memory; if you can assign numbers to them, you should have no problem picking tempos out of the air pretty exactly.
That's what I do, and here are some of my references:
74 – Hotel California
80 – We Will Rock You
98 – Eminence Front
105 – We Can Work It Out
120 – Dim All the Lights
125 - Ticket To Ride
139 – Feel Good Inc
145-148 – Molly’s Chambers
150 - All the Small Things
But there's a method to doing it right. You have to obviously be very familiar with the song, and the trick is to 'hear' it in your head... like you're listening to the radio. Don't sing it to yourself... don't tap your foot or try to play the beat... or you'll influence the tempo. Just let it play in your head for a few seconds, a few bars, and mentally lock it in.
Will it be perfect? Well, not every time, but you'll usually get within a few bpm. Anything that needs to be exact should be done with a 'nome.
Also, if you've played something to a click enough times, chances are you know that tempo to repeat it on the fly. But again, it's the same process as above.
Bermuda
Instead of using seconds, which are a pretty abstract reference point, you might try figuring out the tempos of some real familiar recorded songs. You've heard Back in Black, Another One Bites the Dust, Magic Man, or whatever a thousand times- you should be able to pull up their tempos from memory; if you can assign numbers to them, you should have no problem picking tempos out of the air pretty exactly.
This is a good idea, i think of recordings in a known key in my head to work out what note something is so i suppose it could work for tempos too.