Guides

Short guides that explain the questions behind the tools, such as how to write an invoice that gets paid, the difference between markup and margin, and how EMI is calculated. Each guide links to the tool that does the math and shows a worked example you can repeat.

All guides

Break Even Analysis for a Small Business, Step by Step

Break even analysis in plain steps: fixed and variable costs, contribution per unit, a bakery worked to 600 units, a target profit, and several products.
How Compound Interest Works, Explained With One Example

Compound interest explained with USD 10,000 at 6% over 10 years: simple versus compound by year, the formula, compounding frequency and the rule of 72.
How EMI Is Calculated: The Formula, Step by Step

The EMI formula with every symbol defined, a USD 20,000 loan worked by hand to 400.76 a month, the schedule rows, and flat rate versus reducing balance.
How to Add and Remove VAT or GST From a Price

How to add VAT or GST to a price and take it back out, with GBP and AUD examples, a divisor table for 5% to 20%, and the common mistake explained.
How to Calculate Profit Margin, with Examples

The profit margin formula with a worked example, how to set a price from a target margin, gross versus net margin for a cafe, and 3 common mistakes.
How to Set Your Freelance Hourly Rate, With the Math

Work out a freelance hourly rate from a yearly income target: billable hours, expenses, a margin, day rates, project prices and rates for foreign clients.
How to Write an Invoice That Gets Paid on Time

The 9 details every invoice needs, how to word payment terms and when to follow up, with a filled GBP example worked line by line to the total.
Invoice vs Receipt, Quote and Purchase Order Explained

Invoice vs receipt, quote vs invoice and purchase order vs invoice: who sends each document, when, and why, with a comparison table and 3 short scenarios.
Markup vs Margin: The Difference and a Conversion Chart

Markup vs margin explained with one set of numbers, a conversion chart from 10% to 200% markup, the 2 formulas, and a pricing mistake worked through.
What Should a Payslip Include? How to Read One

Each line of a payslip explained, from earnings and deductions to net pay and employer costs, with a gross to net example worked in GBP.