DIY humidity reader?

is there any way to find out the humidity levels in the room without going out an buyin a digi scale one or something. this is my 1st and last grow and im quite close to the end.

ive done ok without one but id be interested to know if u can tell humidity levels any other way.

i have a thermometer. not sure if u can get a reading from the heat in the room.

for around 12 bucks I bought one from lowe's that reads humidity and indoor/outdoor temps (one at the unit itself, the other at the end of it's wired probe). It was worth it just to have an easy way to read the data on a digital LCD.