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Mortgage Principal and Interest Calculator

See the fixed monthly principal-and-interest payment, inspect how the split changes over time, and test optional extra principal against the full amortization schedule.

Mortgage P&I setup

Fixed-rate principal and interest only. Keep escrow and ownership costs separate.

P&I only

Loan amount

Interest rate

Loan term

First payment month

This calculator deliberately excludes property tax, homeowners insurance, PMI, HOA dues, escrow and lender fees so the principal-and-interest mechanics stay transparent.

Monthly principal & interest

Fixed scheduled payment before optional extra principal.

Fixed-rate model

—Scheduled monthly P&I

—First payment principal

—First payment interest

—Balance after payment 1

—Baseline total interest

—Baseline total P&I

—Baseline payoff month

Payment 1

Move to any payment to see how the principal/interest mix changes over time.

Payment #

—Principal this payment

—Interest this payment

—Remaining balance

—Cumulative principal

—Cumulative interest

—Principal share of payment

Extra principal what-if — monthly, yearly and one-time

Extra every month

Start at payment #

Extra every 12th payment

One-time extra

One-time extra at payment #

Extra amounts are modeled as principal-only payments after scheduled interest for that month. Check your lender’s prepayment rules before acting.

—Modeled payoff month

—Modeled total interest

—Interest saved vs baseline

—Months saved

—Extra principal applied

Baseline plan

Remaining balance over time

Baseline is blue. The extra-principal path appears in green when extra payments are entered.

Full date-aware amortization schedule

#	Date	Scheduled P&I	Extra principal	Principal	Interest	Ending balance

Reuse or export this scenario

Keep calculations browser-local or carry the exact inputs into a link/CSV.

Saved scenarios

Up to four mortgage P&I scenarios in this browser.

Planning model for fixed-rate fully amortizing loans. Results do not include taxes, insurance, PMI, HOA, escrow, fees, adjustable-rate resets, lender-specific payment posting rules or prepayment penalties.

How to use this mortgage principal and interest calculator

Enter the loan amount, fixed annual interest rate, term and first payment month. The scheduled P&I payment stays fixed in the baseline model, while the share going to principal rises over time as the outstanding balance falls.

What this calculator includes

The result focuses on principal and interest, with a date-aware amortization schedule, first-payment split, cumulative principal and interest, remaining balance and optional extra-principal scenarios. It is designed to make the loan mechanics visible rather than hide them inside one monthly-payment number.

What P&I does not include

Property taxes, homeowners insurance, private mortgage insurance, HOA dues, escrow deposits and lender fees are not part of principal and interest. Your actual housing payment can therefore be materially higher than the P&I amount shown here.

Extra principal is a what-if, not a lender instruction

Extra-payment scenarios apply additional money directly to principal in the model. Actual lenders can have different posting conventions, prepayment rules or penalties, so verify how your servicer applies additional payments before relying on the projected savings.