The fee is the reason this page exists
An unsecured personal loan is priced by two numbers, and only one of them is advertised. The interest rate goes on the poster. The origination fee comes out of the money that reaches your account, and it is what turns a rate you agreed to into a cost you did not.
The arithmetic is unforgiving on short terms. A fee is paid once, at the start, whatever the term; spread over three years it adds far more to the annual cost than the same fee spread over ten. That is why two loans at the same quoted rate can cost meaningfully different amounts, and why comparing rates alone is not comparing loans.
The page prints what the borrowing really costs a year once the fee is counted. That figure is the rate at which the money you actually receive, and the payments you actually make, balance out.
Where the fee sits
The convention here is the common one: the fee is deducted from the proceeds. You still owe the whole amount borrowed and you still pay the instalment that repays it, and what lands in your account is less.
Some lenders add the fee to the balance instead, so that you borrow it and pay interest on it. That costs more, and the way to price it here is to put the total, loan plus fee, into the amount field. The payment will be the larger one you would actually be charged.
Either way, the amount you need and the amount you should borrow are not the same number. Needing a round sum after a fee of a few per cent means borrowing more than that sum.
What that rate is, and what it is not
It is worked out from the real cash flows: the net amount arriving today, and every scheduled payment leaving after it, on a monthly grid. The search that finds it is the same one the IRR calculator uses, to the nearest ten-thousandth of a per cent.
It is not the annual percentage rate a lender is required to disclose. Those are defined by regulation, in the United States by Regulation Z and in the European Union by the consumer credit directives, and each folds a specified list of charges into the figure and rounds by its own rules. This page contains exactly the interest and the fees you typed in. Where the lender's disclosed figure is higher, the difference is charges this page never asked about.
What a personal loan brings that this page leaves out
Rates are set by credit assessment, so the rate you are offered can differ from the rate advertised and the difference is the point of the application. Nothing here estimates it, and no calculator honestly can.
Also absent: payment protection insurance sold alongside the loan, late fees, the effect of a missed payment, early repayment charges where they exist, and any variable rate. The schedule assumes a fixed rate paid as agreed.