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Schedule, extras & crossover

Mortgage Amortization Calculator

This calculator builds a fixed-rate mortgage amortization schedule from home price, down payment, rate, and term using the standard annuity payment formula. It models extra monthly paydown, annual and one-time lump sums, simplified accelerated bi-weekly principal, and PMI until loan balance reaches 80% of home price. It outputs interest saved, payoff horizon, principal crossover month, chart, and full schedule—not PITI or ARM rates. Illustrative only; not a loan offer or financial advice.

By Jeff Beem

Updated

01

Home & down payment

$
$
%
Down payment

$100,000

Loan amount

$400,000

LTV

80%

02

Loan terms

03

Extra paydown

$

Recurring principal

$

Once per year

$

Single extra principal

1–360

~13 full payments per year; can shorten a 30-year loan noticeably.

Interest savings vs. baseline
$111,892

Same loan without extra principal or bi-weekly boost

Time shaved

5y 7m

Interest ratio

1.00×

Payoff horizon

24.4 yr

Monthly P&I

$2,528

Principal crossover

June 2041

Month 179: principal share first exceeds interest.

Savings & equity path

Charts compare your accelerated balance path to the standard schedule and show principal vs. interest by year.

Total loan cost
$798,286
Principal
$400,000
50%
Interest
$398,286
50%
Interest saved
$111,892
Extra principal vs. the standard schedule on the same term.
Year 1 payment split
Interest79%
In year 1, 79% goes to interest, 21% to principal
Total cost breakdown
Principal50%
Over the life of the loan, 50% goes to principal, 50% to interest

Reading your results

Home price and down payment set loan amount and LTV. Extra paydown fields change the accelerated path; panels and the table compare that path to the no-extras baseline.

Example: $500k home, $200/mo extra → ~$112k interest saved

Defaults: $500,000 home, $100,000 down ($400,000 loan), 6.5%, 30-year term, $200/mo extra principal. Baseline P&I ≈ $2,528; lifetime interest without extras ≈ $510,000. With $200/mo extra, payoff ≈ 24.4 years, interest saved vs. baseline ≈ $112,000, and Time shaved ≈ 5 years 7 months. At 20% down, PMI stays off.

Interest savings vs. baseline panel

Green block: dollars saved vs. the same loan with all extra fields zeroed. Monthly P&I is the fixed payment before extras; extras appear as additional principal in the schedule.

Amortization schedule toggle

Under Savings & equity path, switch the table between annual summary and monthly rows (beginning balance, payment split, PMI column when LTV started above 80%).

Mortgage amortization schedule with extra payments

Fixed-rate P&I from the standard amortization formula, plus optional extras, PMI when LTV exceeds 80%, and a full payment schedule.

What this calculator returns

Inputs are home price, down payment, annual rate, term, and optional accelerators. Outputs include baseline monthly P&I, interest saved vs. no extras, payoff horizon, principal crossover month, PMI totals when applicable, a balance chart, and an amortization table. Fixed-rate P&I only—no taxes, insurance, HOA, ARMs, or lender-specific bi-weekly drafts.
  • PMI model:
    Monthly PMI ≈ (loan × PMI rate ÷ 100) ÷ 12 while balance ÷ home price > 80%. Not the same as every servicer’s 78% auto-cancel timeline.

How the math works

Fixed monthly P&I uses the ordinary annuity formula on loan amount after down payment. Each month, interest = remaining balance × (annual rate ÷ 12); the rest of P&I (plus any extras) reduces principal.
M=P⋅i(1+i)n(1+i)n−1M = P \cdot \frac{i(1+i)^n}{(1+i)^n - 1}
On $400,000 at 6.5% for 360 months, M ≈ $2,528 and lifetime interest ≈ $510,000 without extras. With no extras, principal crossover is around month 233 on that baseline; default $200/mo extra moves crossover earlier because the balance falls faster.

Extra payments and PMI in this form

Section 03 fields map directly to the schedule:
  • Extra monthly ($):
    Default $200; applied to principal every month after P&I.
  • Annual lump sum / One-time payment:
    Applied in the selected calendar month each year or once at One-time payment month (default month 12).
  • Accelerated bi-weekly:
    Adds standardPI ÷ 12 to principal each month (one extra payment per year).

Mortgage Amortization FAQ

What does this amortization calculator show?

A month-by-month principal and interest schedule from home price, down payment, rate, and term, with optional extras and PMI when LTV starts above 80%. Result panels compare your accelerated path to the baseline and flag principal crossover and PMI drop-off.

What is the principal crossover point?

The first month the scheduled principal portion of P&I exceeds interest on the remaining balance. With form defaults (including $200/mo extra), the Principal crossover card usually lands around month 179. Turn off extras to see the standard-schedule crossover, which is much later on a 30-year loan.

How do extra monthly payments change the schedule?

Everything in Extra monthly ($) goes to principal after P&I. The Interest savings vs. baseline and Payoff horizon panels update instantly. See the educational example card for default-dollar outcomes at $500k home / 20% down / 6.5% / 30 years.

When does PMI drop off in this model?

When starting LTV is above 80%, enter PMI rate (% annual). The schedule stops PMI once loan balance ÷ home price is at or below 80%. At exactly 20% down, PMI stays off. Real lenders may use 78% auto-cancel rules or require an appraisal at 80%—this tool uses the 80% balance threshold only.

What does accelerated bi-weekly do here?

It adds one extra P&I payment per year, spread as monthly principal (standardPI ÷ 12). That is a simplified model, not a lender’s true bi-weekly draft calendar. Toggle it and compare Time shaved to monthly extras only.

How is this different from the main Mortgage Calculator?

The main mortgage calculator adds property tax, insurance, and HOA to monthly P&I. This page is schedule-first: chart, crossover, and a full amortization table with extra-paydown fields. It does not output PITI totals.

Sources & citations

References used for the calculation method and definitions. Links open in a new tab when available.

[1]
CFPB: Understand Loan Options

Overview of fixed-rate amortization and how payments split between principal and interest.

[2]
CFPB: What Is Private Mortgage Insurance (PMI)?

PMI cancellation at 78–80% LTV and borrower request rules.

Financial Estimation Note

General Projections: Results are mathematical estimates based on the rates and formulas currently loaded for this tool, including year-specific tax data where noted. They are intended for high-level planning only.

No Advice Provided: This site does not provide financial, tax, or legal advice. Using this tool does not create a client-advisor relationship with CalcRegistry.

Confirm Numbers: Financial laws change frequently. Please verify all results with a qualified professional (CPA, Financial Planner, or Lawyer) before making significant financial decisions.

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