Investment Return API

Investment return analysis as an API, computed locally and deterministically. The cagr endpoint computes the compound annual growth rate, (end/begin)^(1/years) − 1 — the single constant yearly rate that turns a starting value into an ending value — along with the total return and growth multiple, or runs the other way to project an ending value from a CAGR. The doubling endpoint gives how long an investment takes to double at a given rate, both the exact figure ln(2)/ln(1+r) and the quick Rule-of-72, -70 and -69.3 estimates, or inverts it to the rate needed to double within a target time. The real-return endpoint applies the Fisher equation, real = (1+nominal)/(1+inflation) − 1, to strip inflation out of a headline return — or works backwards to the nominal return needed for a target real return — showing how the rough nominal-minus-inflation shortcut drifts at higher rates. Everything is computed locally and deterministically, so it is instant and private. Ideal for fintech, robo-advisor, portfolio and personal-finance app developers, return and retirement calculators, and finance education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This analyses a lump-sum return; for regular-deposit savings projections use a savings API and for loan amortization a loan API.