How do I use this calculator?
This calculator estimates the principal-and-interest (P&I) monthly payments for a 2/1 temporary buydown. Enter the loan amount, the note (final) interest rate, and the total loan term (in months), then click Calculate.
Calculator Operations:
- Enter the Principal Loan Amount, Note (Final) Interest Rate (APR %), and Total Number of Monthly Payments (e.g., 360 for a 30-year loan).
- Click Calculate to see the estimated Year 1 payment (note rate minus 2 percentage points), Year 2 payment (note rate minus 1 percentage point), and the Year 3+ payment at the note rate.
- The calculator also estimates the total buydown subsidy needed for the first two years (the difference between the note-rate payment and the reduced payments, summed over 12 months for each year; shorter terms are handled automatically).
- Use Reset to clear the inputs, outputs, and calculation steps.
Note: This calculator shows principal-and-interest (P&I) payments only. Property taxes, homeowners insurance, mortgage insurance, and HOA dues are not included.
Enter the principal loan amount, the note (final) interest rate, and the total number of monthly payments into the calculator to estimate the Year 1, Year 2, and Year 3+ monthly principal-and-interest payments for a 2/1 temporary buydown.
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2/1 Buydown Formula
The standard fixed-rate monthly principal-and-interest payment formula is:
Payment = P × i × (1 + i)^N / ((1 + i)^N − 1), where i = (APR/100)/12 and N is the total number of monthly payments.
For a 2/1 temporary buydown, the Year 1 payment is calculated using an APR that is 2 percentage points below the note rate, the Year 2 payment uses an APR that is 1 percentage point below the note rate, and the Year 3+ payment uses the note rate (all calculated over the original term N). The estimated buydown subsidy for the first two years is (Note Payment − Year 1 Payment) × 12 + (Note Payment − Year 2 Payment) × 12 (adjusted if the loan term is shorter than 24 months).
Variables:
- P is the principal loan amount
- APR is the annual interest rate (as a percentage, e.g., 6 for 6%)
- i is the monthly interest rate (APR/100/12)
- N is the total number of monthly payments (e.g., 360)
What is a 2/1 Buydown?
A 2/1 buydown (more precisely, a 2/1 temporary buydown) is a mortgage pricing arrangement that reduces the borrower’s required monthly principal-and-interest payment for the first two years. The reduced payments are commonly calculated as if the interest rate were 2 percentage points lower in Year 1 and 1 percentage point lower in Year 2 compared with the loan’s note (final) interest rate. The note rate itself is typically fixed and does not “adjust” because of the buydown; instead, the payment reduction is usually covered by funds paid at closing (often by the seller or builder) and held in a buydown escrow. After the first two years, the borrower’s payment steps up to the regular payment based on the note rate for the remainder of the term.
How to Calculate 2/1 Buydown?
The following steps outline how to calculate a 2/1 temporary buydown (principal-and-interest only).
- Determine the loan amount (principal), the note (final) interest rate (APR), and the total loan term in months (N).
- Compute the Year 1 buydown rate as (note APR − 2 percentage points) and the Year 2 buydown rate as (note APR − 1 percentage point). If either result is below 0%, use 0%.
- Use the standard mortgage payment formula to calculate three payments (over the same total term N): one using the Year 1 rate, one using the Year 2 rate, and one using the note rate (Year 3+).
- Estimate the buydown subsidy needed by summing the monthly differences between the note-rate payment and the reduced payments over the first 12 months (Year 1) and next 12 months (Year 2).
Example Problem :
Use the following variables as an example problem to test your knowledge.
principal loan amount ($) = 300,000
note (final) interest rate (APR %) = 6.0
total number of monthly payments (N) = 360
calculated monthly payment at note rate (Year 3+) ($) ≈ 1798.65
calculated monthly payment in Year 1 at (APR − 2 points) = 4.0% ($) ≈ 1432.25
calculated monthly payment in Year 2 at (APR − 1 point) = 5.0% ($) ≈ 1610.46
estimated total buydown subsidy for first 2 years ($) ≈ (1798.65 − 1432.25)×12 + (1798.65 − 1610.46)×12 ≈ 6655.08
