Calculator & Utility Guides
Practical explanations for the ten free tools. Choose a guide to see the formula, a worked example and the limitations. Updated October 9, 2026.
- Profit Margin Calculator
- Break-Even Calculator
- Freelance Rate Calculator
- Discount Calculator
- ROI Calculator
- Customer Acquisition Cost
- Conversion Rate Calculator
- Ad Revenue Calculator
- Word & Character Counter
- JSON Formatter & Validator
Monetary tools display USD. You may use GBP, CAD or AUD inputs consistently; the numeric result stays in that currency even though the display label is USD. No exchange rate is applied.
Profit Margin Calculator
How to use it
Revenue minus cost gives gross profit. Divide gross profit by revenue and multiply by 100 to find margin. Markup uses cost as its denominator instead.
Worked example
Revenue of 1,000 and cost of 650 produce profit of 350, margin of 35% and markup of 53.85%.
What to watch for
Use costs that match the revenue period. A gross margin calculation usually uses cost of goods sold; including all expenses produces a different profit measure. Zero revenue cannot produce a meaningful percentage margin.
Break-Even Calculator
How to use it
Subtract variable cost per unit from selling price to find unit contribution. Divide fixed costs by contribution and round up to a whole unit.
Worked example
Fixed costs of 10,000, price of 50 and variable cost of 20 require 334 units; revenue at that rounded threshold is 16,700.
What to watch for
Price must exceed variable cost. This model assumes consistent prices, costs and product mix. For multiple products, use a representative weighted contribution rather than one product’s margin.
Freelance Rate Calculator
How to use it
Divide annual revenue target by working weeks times billable hours per week. Billable hours are paid client hours, not every hour you work.
Worked example
A target of 90,000 over 46 weeks at 25 billable hours per week gives 1,150 billable hours and an hourly rate of 78.26.
What to watch for
Revenue is not take-home income. Include overhead, unpaid time and the reserve you need in your target; allow separately for taxes. Do not enter more than 52 working weeks in a one-year scenario.
Discount Calculator
How to use it
Multiply original price by one minus discount divided by 100. Savings equal original price minus sale price.
Worked example
An original price of 120 with a 25% discount becomes 90, saving 30.
What to watch for
Enter discounts from 0 to 100. Two successive discounts do not add: 20% then 10% leaves 72% of the original price, equivalent to 28% off. Tax and shipping are excluded.
ROI Calculator
How to use it
Subtract investment cost from the ending value or attributable revenue, then divide the difference by investment cost and multiply by 100.
Worked example
Value of 15,000 against investment cost of 10,000 gives a net return of 5,000 and ROI of 50%.
What to watch for
Use consistent periods and include relevant costs. If entering revenue for a campaign, include fulfillment costs in the cost basis or the result can overstate profit. This is a simple ROI, not an annualized return.
Customer Acquisition Cost
How to use it
Divide acquisition-related spending by newly acquired customers in the same measurement period.
Worked example
Spending of 2,500 for 50 new customers gives a customer acquisition cost of 50.
What to watch for
For full CAC, include relevant sales and marketing costs, not only ad spend. Counting leads instead of paying customers produces a cost per lead. Compare CAC with customer contribution and retention, not just revenue.
Conversion Rate Calculator
How to use it
Divide conversions by visitors and multiply by 100. Use the same period and a consistent definition of a conversion.
Worked example
250 conversions from 10,000 visitors gives a conversion rate of 2.5%.
What to watch for
For a visitor-to-customer rate, count converted visitors once. An event-based measure can exceed 100% when one visitor triggers several events; label that measure clearly. Small samples can fluctuate substantially.
Ad Revenue Calculator
How to use it
Divide monthly pageviews by 1,000 and multiply by page RPM. Page RPM means revenue per thousand pageviews, rather than ad impressions.
Worked example
100,000 monthly pageviews at a hypothetical page RPM of 5 gives estimated monthly revenue of 500.
What to watch for
The example RPM is an assumption, not a forecast for any country. Actual revenue varies with audience, traffic source, consent, ad blockers, seasonality and ad inventory. This tool does not measure or create real ad income.
Word & Character Counter
How to use it
The tool counts whitespace-separated words, JavaScript string characters and characters after whitespace removal. Reading time uses 220 words per minute rounded up.
Worked example
The text “Make useful things” contains 3 words, 18 characters including spaces and 16 without spaces. Its estimated reading time rounds to 1 minute.
What to watch for
Hyphenated text without spaces counts as one word. Emoji may count as multiple JavaScript characters; this is not a grapheme counter. Sentence counting is not currently provided. Reading speed varies with content and reader.
JSON Formatter & Validator
How to use it
Paste strict JSON and run the tool. It parses the text and prints valid JSON with two-space indentation. Invalid input produces a parser error.
Worked example
The input {"name":"Masa","tools":10} is printed with each property on its own indented line. A trailing comma is invalid JSON.
What to watch for
JSON requires double-quoted keys and strings and does not allow comments. This tool checks syntax, not a business schema. Formatting can normalize number representations, and very large integers may lose precision. Keep a copy of the original before using the result.