Guides

The sales tax formula with a worked example and how to estimate tax before you buy.

Recover the pre-tax amount from a tax-inclusive total and avoid the subtraction mistake.

Calculate VAT from net or gross prices, reverse VAT correctly, and avoid common percentage mistakes.

Calculate percentage increase or decrease, reverse a percentage change, and understand percentage points with practical examples.

The ROAS formula, a worked example, and how to interpret the result.

Why there is no universal good ROAS, and how to find your break-even ROAS.

Calculate CAC step by step, learn which costs to include, and compare acquisition cost with customer lifetime value.

Calculate conversion rate step by step and learn how to interpret it alongside acquisition cost and advertising return.

Calculate cost per click step by step and learn how to interpret CPC alongside conversion rate, CAC, and ROAS.

Calculate cost per 1,000 impressions step by step and learn how to interpret CPM alongside CPC, conversion rate, and ROAS.

Set a target ROAS from your contribution margin and profit goal instead of relying on arbitrary advertising benchmarks.

Find the minimum ROAS needed to cover advertising from your contribution margin, with examples and practical guidance.

How ROI and ROAS differ, with formulas and when to use each metric.

The difference between markup and margin, with formulas and a worked example.

Calculate profit margin step by step with the formula, a worked example, and common mistakes to avoid.

Calculate customer lifetime value step by step and use LTV with CAC, retention, and margin to evaluate customer economics.

Calculate break-even units and revenue step by step using fixed costs, variable costs, selling price, and contribution margin.

Calculate return on investment step by step and learn how to interpret ROI alongside profit, time, ROAS, and break-even analysis.

Calculate Amazon FBA profit and margin step by step, including product cost, fees, shipping, advertising, and other variable costs.

Calculate markup percentage and selling price, compare markup with margin, and avoid common pricing mistakes.

Calculate compound interest step by step and understand how rate, time, frequency, and contributions affect growth.

Calculate a fixed monthly loan payment step by step and see how rate, term, and fees affect borrowing cost.

Annualize hourly, weekly, biweekly, semimonthly, or monthly earnings with practical formulas and examples.

Convert annual salary to an hourly equivalent using your weekly hours and paid weeks, with practical examples and adjustments.