Found another tool I can highly recommend, although it's not exactly a physical tool, but it's one I've used on just about every single build I've done!!!
I have been trying to use some less expensive motors from Amazon because family has given me gift cards; problem is, I don't know much about matching props and ESCs and such together.
Here's where Ecalc came in. They have a demo version that gives you access to SOME batteries/motors, and it gives you an idea of benchmarks for power usage and what will burn up and what won't. Paying for an annual subscription unlocks the full version, and that has been a HUGE help to me in deciding props, motors, ESCs, etc.
DEFINITELY something to add to the toolbox - link is out at
https://ecalc.ch, and for the annual cost, it's saved me headaches galore on worrying about underpowered or overpowered equipment.
It's not perfect; a Watt meter gives me a better reading on how much actual power is being used. But, at least I can get close BEFORE I buy something, and not have spent $50 on a motor that's really meant for a much bigger plane than what I have!