Extra mortgage vs investing

Guaranteed coupon vs expected return on the extra dollars. Type the rate on your payoff letter — default 7% is the extra-principal file, not today’s lock. Freddie Mac PMMS printed 6.71% the week of September 3, 2026; that is an average of applications. Primer: refi vs extra principal. Sequence: 12-step playbook. Do not rebuild the HELOC vs cash-out tap here.

Quick answer: This calculator compares sending extra principal to a loan with investing the same dollars at a return you type. The sample coupon is an example. The calculator is the All Access tool already described on this page.

The loan

Remaining balance ($) Coupon % (your payoff letter, not PMMS) Years left Extra principal / month ($) Monthly PMI still drafting ($) Original value for 80% PMI drop ($)

The other pile

Expected invest return % (example, not a forecast) Horizon (years) Federal marginal % Share of interest you actually itemize %

0 = 2026 standard deduction ($16,100 single / $32,200 MFJ, Rev. Proc. 2025-32). 100 = you itemize every dollar of qualified residence interest. After-tax coupon ≈ rate × (1 − federal × this fraction).

Extra vs invest

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Educational estimate. Extra equity at the horizon is remaining balance without extra minus remaining with extra — house appreciation hits both. Investing is expected, volatile, and wrapper-dependent. PMI drop is 80% of the original value you typed (Homeowners Protection Act request; automatic is typically 78% if current). Do not cash-out a cheap first lien to “invest the spread” — that file is HELOC vs cash-out. Paid sequence: extra vs investing playbook. Break-even months: refi guide.

What this means for you

What this means for you: extra principal earns the after-tax coupon this model computes, which is a guaranteed save of interest on that loan. The invest side earns the return you typed, which can miss. PMI drop and itemizing are only in the result if you fill those fields.

How to use this calculator

Open the Extra mortgage vs investing and keep the sample numbers or replace them with your own. The result updates as you type.
Read the headline figure first, then the breakdown or chart under it.
Use Copy share link if you want those inputs in the URL. The page is an educational estimate, not a filing, approval, or recommendation.

FAQ

Does extra principal or investing always win?

Neither always wins. The page compares the coupon you typed with the return you typed over the horizon you typed.

Is the default coupon today's mortgage rate?

No. The page says the default is an example and points at a Freddie Mac print separately. Type the rate on your payoff letter.

Does this model a cash-out refinance?

No. Tapping equity with a new first lien or a HELOC is the other housing calculator.

Educational, not financial advice. Page updated October 24, 2026 — no tax, limit, or rate figure was changed in this review.