Finding your FTP

Some of these indoor trainers seem to be giving very high numbers - maybe flattering the users to keep them using them! It should be pretty easy to get a real-world figure very similar to an indoor trainer as long as you pick your route carefully.

Back to the original question you could consider hiring a powermeter, it's fairly inexpensive and if you hired it 2-3 times a year you could keep track of your progress.

you could get a friend or shop to test you....even if you dont have one. 

I cant replicate my indoor power outdoors so well. I have direct drive Kickr, with an ftp 340W from TrainerRoad ,but find it difficult with dodging potholes and general road furniture.  I dont bother using a PM outdoors anymore and just train to improve the indoor numbers.

You can find your FTHR without a PM.. which is a good marker for measuring your efforts.

A power meter isn't the be and end all of bike training although certainly nice to have one, I quote someone cleverer than I.. "A power meter is like a speedometer in a car telling us how fast we are going, whereas a heart-rate monitor is more akin to a rev counter telling us how hard we are working."

If you really want to know your FTP, then get yourself down a gym and sit on a wattbike. But without a PM to measure against, then it's a pretty meaningless metric.

Not really, as there is no other way of measuring power reliably out on the road.  I use 'virtual power' via TrainerRoad which is useful for relative efforts during turbo sessions, but again limited potentially by the viscocity of the turbo fluid changing over the course of a session.  I have however found it helpful for equating perceived exertion with power, which is usable on the road.

You could do an FTP test with a heart rate monitor, and from this get your FTHR.  Usefulness limited by cardiac drift and other HR factors, but I find it a helpful guide out on the road to pace efforts.

I suppose over a flat route, with no wind and evenly paced, the Strava estimated power measure would be in the ballpark, but obviously only useful for measuring power after the ride as its not displayed real time.

I found trainer ftp and real world ftp were about 15% skewed in favour of the turbo trainer. Just too many variables on the road causing ease off situations.

Yes, sort of.  If you have a turbo trainer with a speed/power curve that is supported ny Zwift or similar you can get an estimate of your FTP from that.  Accuracy will probably be dubious but if you're just doing internal comparisons i.e. am I generating more/less power than before, then you would probably find it useful.  Am I generating more/less power than someone else - different story.

You could use virtual power estimates from trainer road but an FTP based on that is only applicable to indoor training.

In a word, no.

More to the point, without a power meter, why would you need it? 

To be fair, if you find an hours cycling route, give it absolute beans and record it on Strava, strava will give you an estimation that shouldn't be a million miles off.