The premium is the whole story
An FHA loan exists so that a smaller deposit and a thinner credit record can still buy a house. The government carries the risk, and the borrower pays for that in insurance: a premium taken at the start and added to the loan, and another charged every year for as long as the rules say.
The rate on the annual premium is not one number. It is read from a published table by three things at once: whether the term is longer than fifteen years, whether the loan is above the national conforming limit, and how the loan-to-value stood at the start. Most calculators pick one rate and use it for everything, which is right for the common case and wrong for the rest.
The line at ninety per cent, and what it decides
The regulation says the annual premium runs for eleven years when the loan started below ninety per cent of value, and for the whole term when it started at ninety or above. That is one sentence and it is worth an enormous amount of money.
The consequence catches almost everyone. At the statutory minimum deposit the loan starts above ninety per cent, so the premium never stops on its own. It is charged for thirty years, and the only ordinary way out of it is to refinance into a different kind of loan altogether.
This is the point where an FHA loan differs most sharply from a conventional one. A conventional borrower's insurance ends automatically when the scheduled balance falls far enough, and can be cancelled earlier on request. Neither applies here: there is no request, and there is no balance that ends it.
How much can be borrowed
The statute puts an FHA loan between a floor and a ceiling, both worked out from the conforming loan limit, and the actual limit in any one place is set between them by local house prices. HUD publishes that county by county.
The two figures shown here are the statutory bounds rather than a lookup of your county, and the page says so rather than implying more precision than it has. For most purchases the floor is the number that binds, and anywhere expensive it will be higher.
What this page does not model
Closing costs, seller concessions, the 203(k) rehabilitation programme, streamline refinances, and the separate arrangements for Hawaiian Home Lands and Indian Lands are all outside it. So is qualifying: the credit assessment, the debt-to-income tests and the property standards are where most applications actually turn, and none of them are arithmetic.