THE LIBRARY
All calculators
Browse practical tools by topic, or search for the calculation you need.
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Break-Even Calculator
Estimate the number of units needed to cover fixed costs. The selling price must exceed variable cost; this simplified model assumes constant unit economics.
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Markup Calculator
Calculate a markup amount and selling price by applying a percentage to cost. Markup is based on cost and is not the same as profit margin.
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Profit Margin Calculator
Calculate profit and profit margin as a share of revenue. Use consistent accounting periods and include the cost items relevant to your margin definition.
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ROI Calculator
Calculate return on investment as net gain or loss divided by the original investment cost. The percentage excludes timing, taxes and other cash flows.
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Simple Interest Calculator
Estimate simple interest, where interest is calculated only on the original principal. This does not model compounding, fees or changing rates.
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Ratio Calculator
Express the relationship between two amounts as a quotient. The second amount must be non-zero; units should be compatible for a meaningful comparison.
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Average Calculator
Calculate the arithmetic mean of three values. Add the values and divide the sum by three; each entry has equal weight.
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Tip Calculator
Calculate a tip, the combined bill and an equal per-person share. The split assumes everyone shares the bill evenly.
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Sales Tax Calculator
Estimate the tax amount and total price after applying one tax rate. Local tax rules and tax-on-tax treatments may differ.
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Discount Calculator
Find the amount saved and the price remaining after a percentage discount. The result excludes shipping, additional taxes and store-specific fees.