How to Calculate a Loan Amount

“How much can I borrow?” has more than one answer. A lender will look at what you can afford to repay, at how much of the property’s value they’re willing to lend, and at the limits of the loan program. This guide shows how to calculate a loan amount each way, with formulas and worked examples, and explains why the smallest of the three is the one that matters.

Method 1: from the payment you can afford

If you know the monthly payment you can handle, the loan amount is the present value of those payments:

loan amount = payment × (1 − (1 + r)^−n) ÷ r

r is the monthly interest rate (annual rate ÷ 12) and n is the number of payments.

Example: you can afford $450 a month on a 5-year car loan at 7%.

Monthly rate: 0.07 ÷ 12 = 0.005833. Payments: 60.
Loan amount: 450 × (1 − 1.005833⁻⁶⁰) ÷ 0.005833 = $22,725.90.

On a financial calculator, enter N = 60, I/Y = 7, PMT = −450, FV = 0, and compute PV. The finance calculator does the same online.

Method 2: from a loan-to-value limit

Secured loans, such as mortgages, auto loans and home equity lines, limit the loan to a share of the asset’s value:

loan amount = value × maximum LTV
down payment = value − loan amount

Example: a $350,000 home with a conventional 80% LTV limit allows a loan of $280,000, so you need a $70,000 down payment to avoid mortgage insurance. With an FHA loan at 96.5% LTV, the maximum would be $337,750 with 3.5% down, plus FHA mortgage insurance.

Method 3: from your income and debts

Lenders cap your total monthly debt payments as a share of gross income, the debt-to-income ratio (DTI):

maximum payment = gross monthly income × DTI limit − existing debts − housing costs
loan amount = present value of the maximum payment (Method 1)

Example: with $8,000 a month of income, a 43% limit, $600 of other debts and $450 of property tax and insurance, the maximum mortgage payment is $2,390. At 6.5% over 30 years, that supports about $378,124. The loan affordability calculator runs this calculation for you.

Worked example: putting the three limits together

A buyer earning $8,000 a month wants a $350,000 home, at 6.5% for 30 years.

Limit	Maximum loan
Debt-to-income (43%)	about $378,124
Loan-to-value (80%, conventional)	$280,000
Loan-to-value (96.5%, FHA)	$337,750

With a conventional loan, the LTV limit is the binding constraint: the buyer can borrow $280,000, not $378,124, and needs $70,000 in cash. With FHA, the loan could be $337,750, but the payment then includes FHA mortgage insurance. Check the full monthly cost with the mortgage calculator.

Loan amount for a car: price, tax and fees

For a car, the loan amount is what’s left after the down payment and trade-in, with tax and fees added:

loan amount = price + sales tax + fees − down payment − trade-in

A $30,000 car with 7% sales tax ($2,100) and $600 of fees, less a $4,000 down payment, needs a loan of $28,700. If the dealer quotes a lower figure, ask what has been left out. If you’re working from a budget instead, the loan affordability calculator shows how large a loan your income supports.

Loan amount for a personal or business loan

Unsecured loans have no collateral, so there is no loan-to-value limit. The amount depends on your income, credit and the lender’s maximum. A budget of $300 a month for 3 years at 11% supports a personal loan of about $9,163. Business lenders also look at the business’s cash flow, often requiring a debt service coverage ratio of 1.25 or more, meaning profit before debt payments must be at least 1.25 times the loan payments.

Calculating a loan amount in Excel

Excel’s PV function does Method 1 in one line:

=PV(rate/12, months, -payment)

For the car example in Method 1, =PV(7%/12,60,-450) returns 22,725.90. To find the payment for a chosen loan amount instead, use =PMT(rate/12, months, -loan).

Program limits: the fourth cap

Some loans also have a maximum set by the program, regardless of your income or the property’s value:

Conforming mortgage limits cap the size of loans that can be sold to Fannie Mae and Freddie Mac. Larger “jumbo” loans usually need bigger down payments and stronger credit.
FHA limits vary by county, higher in expensive areas.
Federal student loans have annual and lifetime limits by year in school and dependency status.
Personal loans often top out at a lender-set amount, commonly between $35,000 and $100,000.

These limits change, often yearly, so check the current figure for your program and location before you plan around a number.

Checking a lender’s loan amount

When a lender quotes a loan amount, work out which limit set it. If it is DTI, paying off a small debt or adding income may raise it. If it is LTV, only a bigger down payment or a different program will. If it is a program limit, you may need a different loan type. Knowing which cap binds tells you which lever to pull.

How the rate and term change the answer

The same payment buys very different loan amounts:

Longer terms borrow more per dollar of payment, but cost more interest. At 6.5%, going from 15 to 30 years lets the same payment support about 38% more loan.
Lower rates raise the loan amount. Each 1-point drop in the rate lifts what a fixed payment supports by roughly 10–12% on a 30-year mortgage.
Fees financed into the loan raise the amount you owe without giving you more to spend.

To see the payment for a loan amount you’ve chosen, use the loan calculator.

Common mistakes

Using the price instead of the loan amount. Subtract the down payment and trade-in first, and add any tax or fees you’ll finance.
Forgetting the costs on top of the payment. For a home, property tax, insurance and HOA dues come out of the same DTI budget.
Assuming the largest answer is available. The binding limit is always the smallest of the three methods.
Forgetting closing costs. A mortgage needs cash for closing on top of the down payment, so budget for both.
Borrowing the maximum. The highest approved amount often leaves no room for savings or surprises. Choose a loan you can repay comfortably, then compare total interest across terms before you commit.

Frequently asked questions

What is the formula for a loan amount from a payment?

Loan amount = payment × (1 − (1 + r)^−n) ÷ r, where r is the monthly rate and n the number of payments. It is the present value of the payments. $450 a month for 60 months at 7% supports a loan of about $22,726.

What is loan-to-value (LTV)?

LTV is the loan divided by the value of what it buys or is secured by. An 80% LTV limit on a $350,000 home means a maximum loan of $280,000 and a 20% down payment.

Which limit decides my actual loan amount?

The smallest of the three. A lender checks the payment you can afford under its debt-to-income rules, the maximum loan-to-value for the property or vehicle, and the program's loan limits. Whichever is lowest sets your maximum.

Does the loan term change how much I can borrow?

Yes. A longer term lowers the payment for each dollar borrowed, so the same budget supports a bigger loan, but you pay more interest overall.