Loan Balance Calculator

Find how much you still owe on a fixed-rate, fully amortizing loan, along with the monthly payment, principal paid off, and interest paid so far.

Quick Facts

Formula
B = M × [1 − (1+i)^−(n−k)] / i
M is the fixed monthly payment, i is the monthly rate, n is total scheduled payments, k is payments already made.
Amortization
Early payments are mostly interest
As the balance shrinks, more of each equal payment shifts toward principal.
Assumes
Fixed rate, no extra payments
Escrow, PMI, fees, and any extra principal payments are not modeled.

Your Results

Calculated
Monthly payment
-
Fixed principal + interest payment
Remaining balance
-
Balance after payments made so far
Principal paid so far
-
Original amount minus remaining balance
Interest paid so far
-
Payments made so far minus principal paid

Ready

Enter the original loan amount, rate, term, and payments made, then press Calculate.

How the Loan Balance Calculator works

This tool answers the question every borrower eventually asks: how much do I actually still owe? It applies the standard amortization formula used by mortgages, auto loans, and most fixed-rate installment loans to compute the fixed monthly payment and then work out exactly how much of the original principal remains after a given number of payments.

The formula

For an original principal P, a monthly interest rate i (the annual rate divided by 12), and n total scheduled payments (loan term in years × 12), the fixed monthly payment is:

M = P × i × (1 + i)n / [(1 + i)n − 1]

After k payments have been made, the remaining balance is:

B = M × [1 − (1 + i)−(n−k)] / i

If the interest rate is 0%, both formulas simplify: the payment is M = P / n and the remaining balance is B = P − M × k, since there is no interest to separate from principal. The calculator assumes a fixed rate, equal monthly payments, and that every scheduled payment was made on time with no extra principal added.

Worked example

Take a $300,000 loan at 6.5% annual interest over a 30-year (360-payment) term. The monthly rate is 0.065 / 12 ≈ 0.005417, which gives a fixed payment of about $1,896.20 per month. After 60 payments (5 years), the remaining balance works out to roughly $280,833 — meaning only about $19,167 of principal has been paid off, even though $113,772 has been paid in total. The other roughly $94,605 went to interest.

Why so little principal moves early on

  • Interest is charged on the outstanding balance: early in the loan the balance is close to the original amount, so most of each fixed payment covers interest rather than principal.
  • The split shifts over time: as the balance shrinks, less interest accrues each period, so a growing share of the same fixed payment goes to principal — this accelerates near the end of the term.
  • Rate and term both matter: a higher rate or a longer term both mean more of each early payment is interest, since a longer amortization schedule keeps the balance elevated for more periods.

What this calculator does not include

This is a pure amortization calculation. It does not account for property taxes, homeowners insurance, private mortgage insurance (PMI), origination fees, or any extra principal payments you may have made. Extra payments reduce the actual balance faster than this formula shows, since the formula assumes only the scheduled payment was made in every period. Use APR rather than the stated interest rate when comparing loan offers, since APR folds in certain fees for a more complete cost comparison.

Frequently Asked Questions

What formula does this loan balance calculator use?
It uses the standard amortization remaining-balance formula: B = M × [1 − (1+i)^−(n−k)] / i, where M is the fixed monthly payment, i is the monthly interest rate (annual rate divided by 12), n is the total number of scheduled payments, and k is the number of payments already made. M itself comes from the standard loan payment formula M = P × i × (1+i)^n / [(1+i)^n − 1].
Why is so little of my early payments going to principal?
Interest is charged on the outstanding balance each period, and early in a loan that balance is close to the original amount, so most of the fixed payment covers interest. As the balance shrinks, more of each equal payment goes to principal — this is normal amortization behavior, not a sign of a bad loan.
Does this include escrow, PMI, or extra principal payments?
No. This calculator models a standard fixed-rate, fully amortizing loan with equal payments and no extra principal, escrow, insurance, or fee charges. Making extra principal payments will reduce the actual balance faster than this formula shows, since it assumes only the scheduled payment was made each period.
What if the interest rate is 0%?
With a 0% rate the payment is simply the principal divided by the number of payments (M = P / n), and the remaining balance after k payments is the original principal minus the principal already paid off (P − M × k), since there is no interest component to separate out.

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