About ToolSimu and how our simulators work

Most calculators answer one question with one number. Real decisions do not work that way: a change in one input moves a chain of other numbers, and the cost that ruins a plan is usually the one nobody put on the spreadsheet. ToolSimu was built to show that chain. Every simulator has five connected stages, a view of the costs above and below the waterline, a 24-month comparison of your current plan with an alternative, and a reverse stress test that finds the exact value at which your result reaches zero.

The aim is understanding, not prediction. We want you to leave with a clearer picture of which lever matters most, how close you are to a breaking point and what questions to ask your accountant, supplier or adviser.

Each simulator starts with a written scope: the decision, the inputs a person can actually know, and the output that matters. We then write the equations in plain code, name every assumption and constant, and give each input a minimum, a maximum and a default. The default is a realistic base case, and we also define an optimistic and a crisis case so you can see the range.

Before a simulator is published it must pass automated checks: the result must be profitable in the base case, better in the optimistic case and negative in the crisis case; worsening any input must never improve the result; the breaking-point search must find a threshold; the 24-month comparison must run; and the guide must be complete in every language. A simulator that fails any check is not shipped.

The domino view follows five stages in order, and each stage is coloured green, amber or red against stated thresholds. The breaking-point search is a reverse stress test: for every input it walks one thousand equal steps from your current value towards the worst end of its range and records the first step where the monthly result crosses zero. The Monte Carlo panel reruns the scenario one thousand times with every input varied randomly by about fifteen percent using a fixed seed, so the same scenario always gives the same answer. The parallel-universe chart compares the cumulative result of your plan with an alternative plan over twenty-four months and marks the month where they cross.

Every formula used is listed in the Formula and methodology blueprint section of the guide under each simulator, and the elasticity paragraph explains which inputs matter most.

The base cases and benchmark tables are illustrative ranges built from general industry knowledge, public documentation and common practice. They are not statistics from a specific survey, and they are not a promise about your results. Money is stored in a neutral base unit and displayed in your language's currency at an illustrative scale, not at a live exchange rate. Wherever a topic depends on changing rules, such as tax, customs duties, carbon border charges or lending terms, the guide says so and asks you to check the current rules.

If you notice an assumption that looks wrong, please tell us. Corrections are reviewed and, when they are right, applied to the simulator and to every language.

ToolSimu is an educational planning tool. It is not a financial adviser, accountant, tax adviser, lawyer, engineer or broker, and nothing on the site is a recommendation to buy, sell, borrow, hire or invest. Use the simulators to prepare better questions, then take important decisions to a qualified professional who knows your situation. The full disclaimer is in the Terms.

All calculations run in your browser. There are no accounts and no database of your scenarios. A shared scenario is stored only inside the link you copy. You can read exactly what is stored on your device in the Privacy policy.

The simulators are free to use. The site may be supported by advertising and by links to paid templates or partner tools. These are always labelled, they never change a calculation, and a simulator's result does not depend on whether a link is configured.

Our editorial rule is simple: the model comes first. A partner or template is shown only when it fits the topic of the simulator and it is never presented as advice.

Simulators and guides are reviewed when we receive a correction, when a rule or price that a model depends on changes in a way we notice, and when we improve the engine. Material changes are applied to all languages together, and the Last updated date on the legal pages shows when the policies last changed.