(miner hashrate) ÷ (network hashrate) × (number of blocks per day) × (block reward).
Or this one below
((Your Hashrate / Network Hashrate) * (Block Reward * Block Time) * Coin Price) - (Price per kWh * Rig kWh Consumption) = Your expected net profit
Or check other formulas suggested here https://bitcointalksearch.org/topic/m.32483696
And why look for paid service if the formula is already shared in Google and here on the forum?
If you are going to develop something then check this opensource one below
- https://bitcointalksearch.org/topic/coin-profitability-calculator-213580