ABOUT SUMLOFT

Tools that teach

A calculator you understand beats one you just trust.

SumLoft builds clean, fast financial calculators for saving, investing, and loans, each paired with a plain-English guide.

Sam OrtegaFinance educator, SumLoft

Sam builds finance tools and writes the explainers that go with them, turning intimidating math into something you can reason about.

How we build

Every calculator is paired with a guide that explains the formula and the assumptions, so the answer is legible, not magic.

Some links to financial products are affiliate links, at no cost to you. The calculators stay neutral.

Every walkthrough follows the same path from the raw formula to a number you can trust.

Start from the standard formulaEach walkthrough is built on the same amortization and compound-growth math our calculators run, not a rule of thumb.
State the assumptions plainlyRates, timelines, and inputs are written out so you can see exactly what drives the result.
Explain the lever, not just the answerEvery calculator is paired with a guide that explains the formula and the assumptions, so the answer is legible, not magic.
Label estimates as illustrativeOutputs are estimates for education, not quotes or financial advice, and we say so on every result.