Make the next business decision with the assumptions visible
Move from customer economics to cash, pricing, margin, break-even, and inventory without creating an account. Every calculator runs locally and states what it leaves out.
Set an inventory trigger that matches operating assumptions.
Decision receipts on these tools can be copied or printed locally. They are summaries—not forecasts or professional advice.
Choose the decision in front of you
Say you run a one-person landscaping crew and keep facing the same fork: rent a stump grinder per job or buy a used one. The toolkit starts by forcing your actual numbers onto the page, not estimates from memory. Suppose your rental invoice runs $150 per day and you booked it 4 days last month, so renting costs about $600 per month. A used unit is listed at $7,000. Ownership is not free, so you list its real monthly costs too — in this example, $100 for maintenance and consumables, $50 for storage and insurance, and a $100 equipment-loan payment taken straight from a lender quote. Owning costs $250 per month in this setup, so buying saves $350 per month and breaks even at $7,000 ÷ $350, or 20 months. None of these are market claims; they are placeholders showing the arithmetic you repeat with your own invoices.
The point of writing the assumptions down is that the answer changes the moment one of them moves. Cut usage to 2 days per month and renting drops to $300, so owning saves only $50 per month — break-even stretches to 140 months, longer than the machine will likely last. At 1 day per month, renting at $150 is cheaper than the $250 ownership cost, and buying never pays off. One assumption — how many days you actually use the tool — flips the decision three times. The toolkit makes you state that assumption, run the math at your best guess and at your worst guess, and only then commit, instead of anchoring on the purchase price alone.
A practical sequence
Work through the decision in order: cash outlay, recurring costs on both sides, monthly savings, break-even months, then a sensitivity check on the shakiest assumption. Most errors come from breaking that order. The commonest is mixing time periods — an annual insurance premium treated as if it were monthly, or a one-time delivery fee spread over a year it will not repeat. The second is counting savings at your busiest month all year long; utilization that only holds in peak season produces a break-even that looks close but never arrives. A third is leaving your own labor off the ledger: returning a rental, winterizing an owned machine, and driving to pick equipment up are real hours, and if your billable rate is $50 per hour, two hours a month is $100 that belongs in the comparison.
Watch for edge cases that quietly break the math. If your work is seasonal, count break-even in active months, not calendar months — a 20-month payback that spans two off-seasons can really mean three buying seasons away. If you are financing, use your actual quoted rate and term rather than a guessed figure, and remember rental prices usually include maintenance while ownership does not, so damage waivers and delivery fees belong on the rental side of the ledger. If the purchase would also unlock a new service line, separate the two effects: decide the replace-the-rental question on savings you have already earned, and treat the new revenue as a separate bet with its own assumptions. Finally, ignore sunk costs — the relevant question is what you would do today knowing what you know, not what you paid last spring.