Do Bitcoin calculators give a realistic figure on pool mining Bitcoin calculators give an approximate correct range reward for solo mining, do they include pools, accounting your Hash rate reward share. I have not seen any pool calculators around, nevertheless their incomprehensible reward systems.
Regardless of whether you're solo mining or pool mining, as long as it's the same coin, your expected number of coins per day should be the same (minus a pool fee). However, the benefit of mining in a pool is that you reduce variance greatly. For example, let's say you have enough hashrate to mine 1 LTC per day on average. If you solo mine, the expected time to find a block is 50 days, but that doesn't mean you will find a block in 50 days. In fact, you might not even find a block in 500 days. It's all random. However, if you're using a pool that finds a block every 50 minutes, the probability that it goes for 500 minutes without a block is the same as the probability that you, as a solo miner, go for 500 days without a block. So you can expect more regular payouts with less risk, making the pool fee well worth it in my opinion unless you alone have 1% of the total network hashrate or something.

As for how the estimated number of coins per day is actually computed from your hashrate, see my answer here.