A better estimate starts with a clearer question.

What the tools do

They apply explicit arithmetic to the figures you enter. Your browser calculates the result. There is no account, database, remote calculation API or business-system connection.

Calculation principles

• Consistent scope: use matching periods and units, and use one currency throughout a financial calculation.
• Margin on selling price: when a target margin is requested, the price is cost ÷ (1 − margin). A markup percentage is not interchangeable.
• Contingency and fee: the budget builder shows contingency separately, then applies the production fee to the cost base.
• Overtime: the simple model uses the supplied day rate and included hours. Agreements may use other rules.
• SEM sample size: the research planner applies Westland's published lower-bound method. The bounds do not guarantee model identification, convergence or estimator-specific power; adapt the study design to the estimator and data.
• Tax: tax is only shown as an entered rate where available; the tools do not determine your tax obligations.

Privacy in practice

Calculator inputs and optional project, client and preparer labels are processed locally in the current browser tab. Copy, JSON download and print-ready estimate actions run on your device. The site does not store input values or transmit them to a backend.

Limits and corrections

Outputs are estimates for planning. They are not quotes, market benchmarks, accounting, legal or tax advice. Check the actual scope, licenses, rates, tax treatment, agreements and insurance requirements. If you spot a calculation issue, report it through the project's issue tracker once a public support channel is configured.