Don't know the monthly payment? Enter the UPB, interest rate, and remaining term to calculate it instantly.
Fill in the loan details above and click Calculate to see your monthly payment.
When you're analyzing a note and the seller doesn't know (or won't tell you) the monthly payment, you can calculate it yourself from three numbers: the remaining balance, the interest rate, and how many months are left.
UPB stands for Unpaid Principal Balance — what the borrower still owes today. This is not the original loan amount; it's the current remaining balance after years of payments. Always get a current payoff statement to verify the real UPB before buying.
The monthly payment is the foundation of every other note calculation. Your yield, your offer price, your cash flow — all of it starts with knowing exactly what the borrower pays each month. If a seller gives you a payment that doesn't match the UPB, rate, and term, that's a red flag worth investigating.
This is the rate stated in the original note documents — the rate the borrower agreed to pay when the loan originated. It doesn't change over the life of a fixed-rate note, regardless of what current market rates are doing. If you're evaluating an adjustable-rate note, you'll need to account for any scheduled rate changes separately; this calculator assumes a fixed rate for the remaining term.
Once you have a verified monthly payment, it becomes an input everywhere else on this site — the Yield Calculator, the Offer Price Calculator, and the Comparison Tool all start from this number. Getting the payment right at this step keeps every downstream calculation accurate.
This calculator computes principal and interest only, abbreviated P&I. That is the portion of the payment that belongs to you as the note holder. Many quoted payments are PITI — principal, interest, taxes and insurance — where the servicer collects extra each month into an escrow account and pays the county and the insurer on the borrower's behalf.
The gap is not small. On a modest loan, taxes and insurance can add two to four hundred dollars a month. If a seller tells you the note "pays $1,050 a month" and this calculator says the P&I should be $724, the likely explanation is that $326 of escrow is baked into that figure. Buying a note on the assumption you will receive $1,050 of income when $724 is actually yours is a straightforward path to a deal that underperforms badly.
Ask explicitly: is the quoted payment P&I or PITI? Then ask for the servicing statement that proves it. Escrowed funds are not yours — they are held in trust for the borrower's tax and insurance obligations, and you inherit that obligation along with the note.
Amortization catches new investors off guard because the split between principal and interest is heavily front-loaded. On a 30-year note at 9%, the first payment might be roughly 90% interest and 10% principal. The payment amount never changes, but the proportion shifts gradually until, near the end of the term, almost all of it is principal.
This matters for two practical reasons. First, the UPB on a young note barely moves for years — a seller describing a five-year-old 30-year note as "well seasoned with lots of principal paid down" is describing something that has not really happened. Second, it means the age of the note tells you a great deal about how much of each incoming payment is genuine return versus capital being returned to you. Seasoned notes deep into their amortization return your principal faster but generate less interest income per payment.
The math on this page assumes a fully amortizing loan — one where the payment is sized so the balance reaches exactly zero at the end of the term. Not every note works that way, and the calculator will not match if yours doesn't.
On an interest-only note the borrower pays only the interest, so the UPB never declines and the entire principal comes due at maturity. On a partially amortizing note, payments are calculated against a longer schedule than the actual term, leaving a balloon at the end. Seller-financed notes written informally between private parties sometimes have no coherent amortization schedule at all — just a payment figure two people agreed on.
If your calculated payment does not match the actual payment and you have already ruled out escrow, a modification and a stale UPB, one of these structures is the likely explanation. Get the promissory note itself and read the payment terms rather than trying to reverse-engineer them.
The single most useful habit at this stage is to insist on documentation from a third party. A servicing statement from a licensed servicer shows what the borrower actually paid and when, how it was applied between principal and interest, and what the current balance genuinely is. A spreadsheet a seller assembled themselves shows what they would like you to believe.
If a note is self-serviced with no professional servicer involved — common on smaller seller-financed paper — you are relying on the seller's own records, and you should discount your confidence accordingly and price the extra uncertainty into your offer.
The monthly payment is calculated from the unpaid principal balance, the annual interest rate, and the remaining term in months using the standard amortization formula. Enter those three values above and the calculator returns the principal-and-interest payment, along with total interest over the life of the loan.
Three numbers: the UPB (current unpaid principal balance), the annual interest rate on the note, and the remaining term in months. All three should come from the promissory note itself or a current servicing statement — not from a seller's summary, which may be outdated or may include escrow amounts that are not part of principal and interest.
Remaining term is the number of monthly payments left until the note is fully paid off, not the original length of the loan. A 30-year note originated in 2014 has roughly 216 months remaining as of 2026. Using the original term instead of the remaining term is one of the most common errors and will produce a payment figure that does not match reality.
Most often to verify that the payment a seller quoted actually matches the loan terms they described. A mismatch signals something worth investigating — an undisclosed modification, an outdated balance, escrow rolled into the quoted figure, or a non-amortizing structure. It is also the starting input for calculating yield, offer price, and side-by-side note comparisons.
I use this calculator as a cross-check almost as much as I use it to fill in a missing number. If a seller tells me a note pays $724 a month and I run the UPB, rate, and term through this tool and get something noticeably different, that's a conversation I have before I go any further — not after I've wired money.
In my years around real estate deals, the numbers that don't quite add up are usually the ones worth slowing down on. Sometimes it's an innocent mistake. Sometimes it means the note was modified and nobody mentioned it. Either way, I want to know before I buy, not after.