Tools.
Small calculators for the arithmetic that sits between a trading idea and an actual order. Free, no account, no email, and the answer appears as you type.
Which one you want
Each of these settles a different question, and it is usually obvious which one you are asking.
The position size calculator answers how many shares. You bring the price you would buy at, the price where you would admit you were wrong, and the amount you are willing to lose finding out. It returns a share count. Size is the lever most people leave alone while fussing over the stop, and a tight stop on too large a position still ends badly.
The covered call calculator is for when you already hold at least a hundred shares and are looking at selling a call against them. It shows the premium, the break-even it moves you to, and the price above which the shares get sold. That last number is the one people skip, and it is the whole trade-off.
The option profit and loss calculator covers all four single-leg positions and shows where each one starts making and losing money. Its more useful job is showing which of them are bounded and which are not, because a short call with no shares behind it has no upper limit on the loss and that is not obvious from the order ticket.
The arithmetic is tested
Forty-five checks run against these three calculators on every build, and they pin the worked examples printed in the page copy to the code that produces them. If someone edits a number in the prose without changing the maths, the build fails.
One of those checks is a rule rather than a value: where rounding could go either way, it has to round toward showing more risk, never less. A calculator on a public page should not be capable of telling you a position is smaller or safer than it is.
What they deliberately will not do
None of them suggests a strike, a stop, an expiry or an amount. You supply those. The tools do the arithmetic and stop, because the moment a page picks a number for you it has started giving advice, and that is a line this site does not cross.
The covered call page in particular shows no annualised yield or return percentage. Premium expressed as a percentage per year reads like an interest rate, and it is not one: it is the price of giving up an unknown amount of upside, on a position that can still fall.
Why these are free
Every one of these does something you could do on paper. Putting them behind a signup would be a way of charging for arithmetic, and it would make the page useless to the person who just wants a number before the market opens.
What is worth paying for is the part that happens when you are not watching. That is what the bots do: they apply rules like these on the broker account you already have, while you are at work. The tools here are the manual version of one small piece of that.
These pages are educational. They compute what you enter and do not offer advice or recommendations. See the risk disclosure.