FreeByte

Invest or repay debt calculator

Which use of a spare dollar wins.

Built and reviewed by Dovanic, Founder and editor, FreeByteLast reviewed: 2026-08-18
$
7.5%
7%
15%

Repay the debt

$1,006 better

Investing nets

$3,351

With these inputs, repay the debt comes to $1,006 better over 5 years. Investing nets works out to $3,351. The result assumes debt interest rate stays at 7.5%.

Repaying saves
$4,356
After-tax return
5.95%

Over time · by years

What moves the number · Repay the debt

Input−10%Now+10%
Spare cash$905 better$1,006 better$1,106 better
Debt interest rate$512 better$1,006 better$1,513 better
Investment return$1,376 better$1,006 better$626 better
Tax on returns$939 better$1,006 better$1,072 better
Years$876 better$1,006 better$1,143 better

Solve for an input

Whatmakesequal

Compare scenarios

Save this set of inputs, change something, then save again to compare the outcomes side by side.

Which use of a spare dollar wins.

A worked example

Starting figures

Spare cash
$10,000
Debt interest rate
7.5%
Investment return
7%
Tax on returns
15%
Years
5

What it returns

Repay the debt
$1,006 better
Investing nets
$3,351
Repaying saves
$4,356
After-tax return
5.95%

How to read the results

With the defaults above, repay the debt works out at $1,006 better.

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