The Standard Calculator is one of the most used tools when it comes to matched betting.
This calculator can be used to help with all of your normal, free bet and risk free matched betting calculations. It can be used in Simple mode or Advanced mode, which gives you more flexibility with your lay bet.
The standard calculator has 4 bet types to select, Normal, Free Bet (SNR), Free Bet (SR) and Risk Free. 
Normal is the bet type used for your qualifying bets. You would select this bet type when you are placing your cash bet to qualify for a free bet or offer.
Free Bet (SNR) is used for your free bets. SNR stands for Stake Not Returned. We use this as the calculator factors in that your stake won't be returned if your bet wins at the bookies.
Free Bet (SR) is also used for free bets, however, the SR here stands for Stake Returned. You will rarely, if ever, use this as 99% of bookies do not return the free bet stake, still, it's worth having there, just in case!
The Risk Free bet type would be selected for offers where you get a free bet if your qualifying bet loses. We also have a standalone Risk Free Calculator that does the same thing. You can read more about risk free offers here to get more of an understanding of what they entail.
There are multiple boxes on the calculator, most of which are self-explanatory, but I'll delve into them so it's crystal clear. 
1. Back Stake - this is where you enter the amount you intend to stake at the bookie.
2 .Back odds - this is where you enter the odds of the bet you are placing at the bookies.
3. Bookie Commission - this is often left empty as you don't pay commission at the bookies. Sometimes you will place a back bet at an exchange though, such as Betfair Exchange, and they charge a 5% commission as standard, so in this case, you would enter 5 into that box, to reflect the commission payable.
4. Lay Odds - this is where you enter the lay odds of the bet you are laying at the exchange.
5. Lay Commission - If you pay commission at the exchange you are placing your lay bet with, you need to enter that amount here, often you will pay 0%, such as with Smarkets, so ensure you have this box filled in.
After entering details into the calculator, you will be shown how much you need to lay at the exchange and what your profit/loss is from that bet, as well as a breakdown showing what happens if the bet wins at the bookmakers, or what happens if the lay bet at the exchange wins, see screenshot below. 
There is also an Advanced mode on the calculator. Having the calculator set to Advanced will give you different lay options. When starting out, keep it in simple mode, as the advanced options won't be needed. 
The final thing to note on this calculator is the Part Lays toggle - it is set to hide as standard, but if you click the toggle, it will change to show, and you will see the appearance of the calculator change as an additional pink box is added with part lay stake and part lay odds boxes added. 
This is used when bets are partially matched. It can and will happen at some stage in your matched betting journey, so it's useful to know how to deal with this, should it arise.
This guide explains more about unmatched and partially matched bets, how to try to avoid them, and how to fix them if they do occur.