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What Banks Hide

How much interest is your lender hiding from you?

See the interest your lender buried in the fine print. Calculate exactly how extra payments cut years off your mortgage and save thousands.

Your Mortgage Details

Remaining balance, not original loan amount
Annual rate (national avg ~6.5%)
I know my...
Principal & interest only, not escrow

Extra Payment

$0

Your Current Plan

Time to payoff

30 yr 1 mo

Total interest

$255,191

Total paid

$455,191

Compare Strategies

Your monthly budget impact

For $1,238/mo more, you save $192,839 total and pay off 21 yr 4 mo sooner.

Balance Over Time

Total Cost Comparison

Current Plan
$455,191
$200,000
$255,191
Principal
Interest
+$300/mo
$341,584
$200,000
$141,584
Principal
Interest
+$650/mo
$295,752
$200,000
$95,752
Principal
Interest
+$1250/moBest value
$262,352
$200,000
$62,352
Principal
Interest
Bi-weekly
$396,980
$200,000
$196,980
Principal
Interest
1 extra/year
$399,161
$200,000
$199,161
Principal
Interest
Mortgage Early Payoff
whatbankshide.com
Current payoff30 yr 1 mo
Total interest (current)$255,191
Best strategy: +$1250/mo
Interest saved$192,839
Time saved21 yr 4 mo
New payoff8 yr 9 mo

How It Works

Every mortgage payment has two parts: principal (paying down your loan) and interest (the cost of borrowing). Early in your loan, most of your payment goes to interest. Extra payments go directly to principal, which reduces the balance that accrues interest - creating a compounding savings effect.

The math: Each month, interest = remaining balance × (annual rate ÷ 12). When you pay extra, you reduce the balance faster, so next month's interest is lower. This means more of your regular payment goes to principal too - a virtuous cycle.

The formula: We generate a full month-by-month amortization schedule for each strategy, applying extra payments and recalculating interest each period. No shortcuts or approximations - this is the exact math your lender uses.

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Frequently Asked Questions

Does this include taxes and insurance?
No - this calculator works with your principal and interest (P&I) payment only. Taxes, insurance, and escrow are not affected by extra principal payments. If you only know your total payment, use the helper to subtract your escrow amount.
What about PMI?
PMI (Private Mortgage Insurance) typically drops off once you reach 20% equity, and most lenders are required to cancel it automatically at 22%. Making extra payments gets you to that threshold faster, which can save you additional money beyond what this calculator shows. On a conventional loan, PMI usually costs 0.5-1% of the loan amount per year, so eliminating it early can save $100-200 per month on a $300,000 mortgage.
How do I find my current interest rate?
Check your monthly mortgage statement, your original loan documents, or log into your loan servicer's website. The rate is the annual percentage, not the APR (which includes fees). If you have a fixed-rate mortgage, the rate never changes. If you have an adjustable-rate mortgage (ARM), look for your current rate, not the initial rate, since it may have adjusted since origination.
How does bi-weekly payment work?
Instead of 12 monthly payments, you make 26 half-payments (every two weeks). This equals 13 full payments per year - one extra payment annually. We model the equivalent monthly impact. Read our full guide on biweekly payments at /guides/biweekly-payments-explained.
Is the effective return really comparable to investing?
Yes and no. The mortgage payoff return is guaranteed (you definitely save that interest), while investment returns are not. The effective return shown is a useful comparison point, but remember: mortgage payoff is risk-free while market returns involve volatility.
Should I pay extra on my mortgage or invest?
It depends on your rate, risk tolerance, and tax situation. If your mortgage rate is above ~5%, extra payments are often competitive with market returns on a risk-adjusted basis. Read our complete guide at /guides/should-i-pay-extra-or-invest or try our Extra Payment vs Investing calculator for a full comparison.