Why we built this

BasisCalc started from a simple frustration: most financial calculator sites are either too shallow to be useful or so buried in ads and "get a quote" CTAs that the actual math is an afterthought. We wanted tools built by someone who uses them — someone who actually cares whether the options P/L math accounts for early assignment, whether the cost basis calculator handles multi-lot FIFO correctly, whether the margin interest formula matches what brokers actually charge.

We're investors ourselves. Precision matters to us. When a calculation is wrong or oversimplified, it's not just annoying — it can affect real decisions. So we focus relentlessly on accuracy, clear inputs, and honest outputs.

Why these specific calculators

There's no shortage of basic compound interest or mortgage calculators online. We intentionally built calculators that cover the gaps — the ones mainstream tools like Bankrate or NerdWallet handle poorly or ignore entirely:

• Options P/L — modeling profit, loss, and breakeven across strategies, not just a single call or put.
• Margin interest — showing the true cost of leverage, annualized and day-by-day.
• Cost basis with multi-lot — FIFO, LIFO, and specific lot accounting for investors who actually buy in tranches.
• FEIE for expats — the Foreign Earned Income Exclusion is one of the most under-served calculator categories on the web.
• FX real cost — because the "0% commission" broker still takes a spread, and knowing that number matters.
• Position sizing — risk-per-trade math that traders use every day but rarely find cleanly implemented.

The remaining calculators — DRIP, FIRE, CAGR, Sharpe ratio, and mortgage — round out the toolkit for long-term investors and anyone building toward financial independence.

Who it's for

BasisCalc is built for:

• Active retail investors who want precise answers fast and don't need a dashboard subscription to get them.
• Options traders who need P/L, position sizing, and risk math in one place.
• US expats navigating FEIE, foreign tax credits, and the complexity of US taxes from abroad.
• Anyone tired of bloated finance sites — the ones that make you sign up, accept cookies in a full-screen modal, dismiss three newsletter popups, and then give you a result that's three years out of date.

If you're an institutional trader or looking for real-time data feeds, this isn't that. BasisCalc is a clean, fast reference toolkit — best suited for retail investors doing their own research and math.

What's next

We have more calculators in the pipeline — covering additional options strategies, bond yield calculations, tax-loss harvesting math, and more expat-specific scenarios. We're also working on deeper written guides to sit alongside the calculators, so the math is explained alongside the results.

Down the road, we're considering a simple API for developers who want to embed the calculation logic in their own tools. If that interests you, drop us a note via the Contact page.

Monetization — the honest version

BasisCalc is free to use with no paywalls planned. The site is supported by display ads (currently Google AdSense). We don't sell user data — as explained in our Privacy Policy, calculator inputs never leave your browser.

We may work with relevant affiliate partners (brokers, tools) where there's a genuine fit, and we may do direct sponsorships in the future. If we ever do, we'll be transparent about it. If an affiliate relationship influences a recommendation, it'll be disclosed clearly.

Contact

Questions, feedback, or suggestions? We'd love to hear from you. Reach us at hello@basiscalc.com.

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