You may find this coindesk article helps
http://www.coindesk.com/information/cloud-mining-bitcoin-guide/In addition to work out what you will really earn from mining without using a mining calculator (most of which are based on solo mining and complete nonsense in regards what you will get) use the following formula.
Rough expected reward (per day) = (your hash rate / network hash rate)*(144*25)*(1-%pool fee)
Ex: you have 500TH/s. Network has 20000TH/s. 5% pool fee.
(500/20000)*(144*25)*(1-.05)
(.025)*(3600)*(.95)
Expected return: 85.5BTC/day
Adjust for coin of your choice. You'd get a better immediate estimate by working with difficulty instead of network hashrate, but - eh.
This answer was provided by someone far cleverer than me via
https://bitcointalk.org/index.php?topic=447051.0I have used this formula on different alt coins that I have mined and it is pretty darn accurate. Not 100% but gives a good estimate far more accurate than mining calculators that I used in the past.
Even thought I mine I also use faucets such as
http://freebitco.in/?r=527569 and
http://freedoge.co.in/?r=8875 I use these to get more satoshi to invest into coins; then make profits by speculating on coins that I think will go up in value.
Hope that helps and happy mining.