Free tools
Use free calculators with visible formulas, worked examples and clear limits for finance, conversions, health, business, energy, travel and more.
Calcunia method
Calcunia keeps the main directory focused on tools with a clear intent, visible formula, worked example and explicit limits. Programmatic pages stay out of the standard sitemap until they have been reviewed. This keeps the visible catalogue smaller, but it avoids offering users an inflated collection where several tools repeat the same logic under different titles.
Strong pages explain which values are entered, which operation is used, how to read the result and where the estimate can become fragile. This helps catch unit, period and scope mistakes before a number is reused in a budget, comparison, project plan or conversation with a professional.
Public calculators run in the browser to display an immediate result. Entered values do not require a user account and should be copied separately if you want to keep a simulation. This is useful for quick estimates, but it also means you should keep your own notes when a result needs to be compared later.
Some categories start with one tool because the goal is to avoid an artificially inflated directory. A short category must explain what it covers, what it does not cover and how to use the result without overreading it. New calculators are added when their intent, inputs and limits bring a genuinely different use case.
Examples use concrete amounts, durations, surfaces, units or quantities. They act as checkpoints so users can compare their own values with a completed calculation before drawing a conclusion. A useful example is not decoration; it shows where units, rounding or assumptions can change the result.
Estimates are useful for preparing comparisons. They do not replace a professional, contract, official notice, medical opinion, tax rule or measurement made with the right protocol. If a calculation error could create a cost, commitment or risk, use the result as a first check and confirm it with a qualified source.
For sensitive topics, Calcunia encourages testing several sets of values rather than trusting one output. The most useful result is often the gap between cases, not the isolated number. By changing one input at a time, you can see which assumptions actually control the conclusion.
A calculator directory can become noisy quickly if every minor variation becomes an indexed page. Calcunia favors stable, understandable and verifiable tools. Topics that depend on local rules, regulatory details or highly volatile data are handled cautiously or excluded until they can be explained clearly.
Start with the category closest to your question, open the tool whose inputs match your data, then compare at least two cases. Keep the formula, date, assumptions and result if you want to reuse the estimate in a document or decision.
Interest, loans, investments
Percentages, fractions, algebra
BMI, metabolism, fitness
Length, weight, volume
Margins, VAT, e-commerce
Wages, compensation details
Kitchen measures, portions
Construction, materials
Grades, GPA, studies
Durations, days, counts
Fuel, costs, mileage
Electricity, consumption
5 additional categories are available in the interactive directory after the page loads.