BasisPilot offers free investment calculators for recurring investing (DCA), average cost and break-even, position sizing, stop-loss planning and ETF overlap. No account is required, and the formulas are visible and versioned (v1.0), with assumptions and limitations published. The site says it accounts for fees, slippage, inflation and whole-share rounding.
It is a web tool in English and Chinese, and it does not connect to brokerage accounts. The site provides educational calculations and does not provide personalized investment, tax or trading advice. It also has market research sections, including a scanner, stock pages, 13F and Form 4 filings, news and a briefing.
BasisPilot provides educational investment tools for planning recurring contributions, calculating average purchase cost, sizing positions and exploring stop-loss levels, with the methodology published so the assumptions can be checked.