Owner financing calculator

What this calculator computes

This calculator produces the complete repayment picture for a fully amortizing owner-financed note: the level monthly payment, and a schedule showing every payment split into interest and principal with the running balance after each row, down to an exact final payment. Every figure comes from the same computation engine that runs OwnerNote itself — the page does no arithmetic of its own, so the number you see here is the number the product would track.

What each input means

Principal is the amount financed — the sale price minus the down payment, not the sale price. Annual rate is the note's fixed yearly interest rate; it accepts up to six decimal places, enough for eighth- and sixteenth-point quotes.Term is the number of monthly payments the note amortizes over. Origination date is the day interest starts running, and first payment date is when the first installment is due — on most owner-financed notes that is the first of the following month.

Day count convention deserves the most attention, which is why it is an explicit choice here rather than a hidden default. The convention decides how days are counted when interest accrues, and the two options — 30/360 Bond Basis, where every monthly period counts as exactly one-twelfth of a year, and Actual/365 fixed, where interest runs on real calendar days — produce different interest on the same note. A silently wrong convention is unrecoverable: once payments have been applied under the wrong day count, every allocation and every balance after the first payment is wrong, and no later correction can be made without reworking the entire history. Read the note's payment clause, pick the convention it states, and the result will show which one was used.

A worked example

Take a $150,000.00 note at 8.00% fixed, amortized over 360 months, originated January 1, 2026, with the first payment due February 1, 2026, accruing on a 30/360 Bond Basis day count. The level monthly payment is $1,100.65. Under 30/360 Bond Basis a regular 1st-to-1st month counts as one-twelfth of a year, so payment 1's interest is $150,000 × 8% ÷ 12 = $1,000.00; the remaining $100.65 of the payment goes to principal, leaving a balance of $149,899.35. Each month the interest share shrinks and the principal share grows as the balance falls.

The last row is worth reading carefully. Interest is rounded to the cent once per period and principal is derived from it, so a fraction of a cent of rounding accumulates across the schedule. The engine absorbs that residual into the final payment rather than leaving a stray balance: on this note the final payment is$1,096.41, not the scheduled $1,100.65, and the ending balance is exactly zero. On some notes the final row differs from the scheduled payment by far more than a few dollars, which is why the schedule always shows the final row's actual amount due distinctly instead of printing it as an ordinary row.