Calculators & finance

Abacus

Numbers you can trust.

Abacus is the room where the math happens. Calculators for the decisions that actually move money — mortgages, loans, retirement horizons, tax estimates, rent vs buy — built without the ads, the lead-gen gates, or the rounding shortcuts that plague the usual suspects. Every number shows its provenance: the formula, the inputs, the amortization row, the sensitivity table.

01 · Signature experiences

The math, shown.

5 tools

Live

Mortgage Calculator

PITI monthly + full amortization schedule on a parchment ledger page. Sensitivity strip for rate shifts, URL-shareable state.

Live

Loan Calculator

Auto, personal, student. Same amortization engine with an extra-principal mode that shows what you’d save.

Live

Compound Interest

Investment growth with a year-by-year ledger, inflation toggle, and an inline sparkline of the cumulative curve.