About RecastMath
RecastMath is an independent website with free calculators for the decisions that come after you already have a mortgage: recasting after a lump sum, refinancing, paying the loan off early or investing instead, and clearing a home equity line of credit.
Why this site exists
Most mortgage calculators answer one question: what is my payment? The harder questions come later. Should I put a bonus toward the loan? Is a recast worth the fee? Does a refinance pay for itself before I move? These answers depend on comparing two or three paths side by side, and on assumptions that most tools hide. RecastMath shows every path, every assumption, and every formula.
How the calculators are built
- One tested math library. Every number on the site comes from the same amortization code, which is checked against published reference payments and against invariants such as a 30-year loan retiring in exactly 360 payments.
- Servicer-style rounding. Interest is rounded to the cent each month, the way a servicer posts it.
- Formulas on the page. Each calculator explains its formula and works through an example by hand.
- Your numbers stay in your browser. Calculations run on your device. Nothing you enter is sent to us.
The full standards are in our editorial policy.
What RecastMath is not
We are not a lender, broker, or financial adviser, and we do not sell or refer loans. The calculators are educational estimates. Read the disclaimer before relying on a result.
Get in touch
Found a number that looks wrong? Contact us. Calculation reports are the messages we act on first.