Convertible Note Conversion & Usury Calculator

Model the implied annualized yield on a convertible note at conversion and see whether the structure clears each major state’s usury threshold. For founders, sponsors, and counsel running multi-state rounds.

Note Terms

Principal funded ($)e.g. 250000

Stated interest rate (% per year)simple, e.g. 8

Months to conversionwhen note actually converts

Conversion discount (%)e.g. 20 for 20%

Valuation cap ($)leave blank if uncapped

Priced-round valuation at conversion ($)pre-money or post-money used consistently with cap

Results

Implied annualized yield

—

Accrued interest at conversion—

Note balance at conversion—

Effective conversion price ratio—

Which feature binds—

Equity received (at round price)—

Conversion premium (gain)—

Total return over principal—

Structuring a multi-state convertible round?

This calculator shows directional risk. The drafting around it is where the deals live or die.

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Disclaimer. This tool is provided for general informational purposes only and is not legal or financial advice. The implied-yield math is a simplified directional model; actual usury analysis is highly fact-specific and depends on governing law, the corporate-borrower status of the issuer, the precise instrument design, and authorities not modeled here. The state thresholds shown reflect general civil and criminal usury caps as of 2026 and do not capture every exemption, carve-out, or savings-clause cure. Reading this page does not create an attorney-client relationship with Montague Law. Consult counsel before relying on any output of this calculator.