Small business decisions are math wearing a costume: can this product cover its costs, is that loan worth it, what does this state's tax do to my margins. These tools strip the costume off.
Break-even units: fixed costs ÷ (price − variable cost). It tells you whether a business model works before effort can matter — if the number is implausible for your market, no amount of hustle fixes it. The break-even calculator computes it in seconds.
Start from cost-plus as a floor (variable cost × your target margin), then sanity-check against the break-even units that price implies. A price is only good if the break-even count is realistically achievable in your market.
Compare the loan's total interest cost (loan payoff calculator) against the profit the borrowed money generates (ROI calculator). If the capital earns more than the APR costs, the loan is a tool; if not, it is an anchor.