Learn: calculators
Run your own numbers.
Nothing here is gated. Every calculator shows its formula so you can check the work, and none of them ask for your email before showing a result.
Calculator 01
Monthly payment.
Full PITI including estimated mortgage insurance, plus an amortization summary showing where the first year of payments actually goes.
10.0%, $52,700 down
Montana effective property tax runs roughly 0.6% to 0.9% depending on county mill levies. Change this to your county.
Estimated monthly payment
$3,602
- Loan amount
- $474,300
- Total interest over 30 yrs
- $577,025
What changes if
Your first twelve payments
- To principal
- $5,558
- To interest
- $29,486
- Balance after year one
- $468,742
Early payments are mostly interest. That is amortization, not a fee, and it is the reason an extra principal payment early is worth so much more than a late one.
How this is calculated
Principal and interest use M = P × [ r(1+r)^n ] ÷ [ (1+r)^n − 1 ], where P is the loan amount, r is the annual rate ÷ 12 and n is the number of monthly payments.
Monthly taxes are the purchase price × your county tax rate ÷ 12. Insurance is the annual premium ÷ 12. PMI is estimated at 0.5% of the loan amount per year whenever the down payment is under 20%, and it drops off as you approach 20% equity. HOA is added as entered.
Amortization summary and first-year split.
Enter your loan amount to see how much of year one goes to interest versus principal. Early payments are mostly interest, and seeing that number is the fastest way to understand why extra principal is so powerful in the first decade.
How this is calculated
Monthly principal and interest uses the standard amortization formula: M = P × [ r(1+r) ^n ] ÷ [ (1+r)^n − 1 ], where P is the loan amount, r is the annual rate divided by 12, and n is the number of monthly payments.
The first-year split is computed month by month: interest for each month equals the remaining balance × r, principal is the payment minus that interest, and the balance drops by the principal. Early payments are mostly interest because the balance is still large.
Monthly principal and interest
$2,771
Year one interest paid
$27,976
Year one principal paid
$5,273
Balance after 12 payments
$444,727
You will have reduced the balance by 1.2% in the first year.
Total interest over 30 years
$547,462
Estimates only, for education. Not a quote, not a commitment to lend, and not an offer of credit.
Calculator 02
What can I afford.
Two ceilings, side by side: the 43 percent debt-to-income figure many programs will allow, and the 36 percent figure most people are happier living inside.
Car, student loans, credit card minimums, child support. Not groceries or utilities.
How this is calculated
We take your monthly budget for housing as (gross monthly income × DTI ceiling) − your existing monthly debt payments. Then we solve for the highest purchase price whose full payment fits that budget, where the payment is principal and interest plus monthly taxes, plus one twelfth of the annual insurance premium, plus estimated PMI of 0.5% of the loan amount per year whenever the down payment is under 20%.
Live DTI = (existing debts + resulting housing payment) ÷ gross monthly income. The 43% figure reflects a common program ceiling; the 36% figure is the conservative budget most people are happier living inside.
Maximum purchase price at a 43% DTI ceiling
$466,817
Estimated payment $3,120 per month. Resulting DTI 43.0%.
Maximum purchase price at a 36% conservative ceiling
$379,404
Estimated payment $2,490 per month. Resulting DTI 36.0%.
Down payment applied
$60,000
This is arithmetic, not an approval. Program ceilings vary and compensating factors matter.
Estimates only, for education. Not a quote, not a commitment to lend, and not an offer of credit.
Calculator 03
Refinance break-even.
The only question that matters in a refinance is how long it takes to earn back the cost, and whether you will still be there.
How this is calculated
The new payment is the amortization formula applied to the new principal at the new rate and term. If costs are rolled in, the new principal is your balance plus the closing costs; if not, the principal is the balance and you pay the costs at closing.
Monthly savings = current payment − new payment. Break-even months = closing costs ÷ monthly savings. Lifetime interest for each loan is (payment × months) − principal, with closing costs added to the new loan either way, so a longer term can lower the payment and still cost more overall.
New monthly payment
$2,379
Monthly savings
$361
Months to break even
18 months
About 1.5 years.
Lifetime interest, current loan
$502,760
Lifetime interest, new loan (costs included)
$471,366
$31,394 less interest over the life of the loan.
If you are not staying past the break-even month, the refinance costs you money. We will say so.
Estimates only, for education. Not a quote, not a commitment to lend, and not an offer of credit.
Calculator 04
Extra payment payoff.
What an extra hundred dollars a month, or one good bonus a year, does to your payoff date and your lifetime interest.
Applied once every twelve months. Tax refund, bonus, a good season.
How this is calculated
We amortize your loan month by month. Each month interest equals the balance × (annual rate ÷ 12); the scheduled payment plus your extra amount goes in, interest comes off the top, and everything left reduces the balance. Any annual lump sum is applied on the twelfth month of each year.
Months saved is the scheduled number of payments minus the number it actually took. Interest saved is the scheduled lifetime interest minus the interest you actually pay on the accelerated schedule.
New payoff date
November 2048
Scheduled payment $2,429 plus $250 extra.
Months saved
70 months
About 5.8 years earlier.
Total interest saved
$104,501
Interest paid on this plan
$326,735
Interest paid on the scheduled plan
$431,236
This is usually the highest-return move available to a homeowner and nobody makes a commission on it.
Estimates only, for education. Not a quote, not a commitment to lend, and not an offer of credit.
Want these numbers checked against a real program?
Opens our secure application at bisonteam.floify.com in a new tab. About 12 minutes.
Rates, DTI, PMI, points, closing costs and the Montana specifics.