Help & User Manual

Welcome to the 3-Way Calculator. This manual covers every feature, setting, and use case so you can get the most out of the app.

What is the 3-Way Calculator?

3-Way Calculator is a focused, single-purpose calculator: given any one of Before, After, or Amount, it instantly computes the other two using a configurable flat rate.

• Freelancers and contractors calculating VAT, GST, or sales tax on invoices
• Small business owners working out prices inclusive or exclusive of tax
• Accountants and bookkeepers doing quick tax lookups
• Shoppers and travellers figuring out the final price including local tax
• Anyone dealing with commission, Zakat, tipping, discounts, or margins

The core insight is simple: in most tax systems only one of the three values is known at a time. The calculator removes the mental arithmetic and the rounding guesswork.

The calculator supports two calculation directions:

• Additive mode (+) — the percentage is added (VAT, commission, tips)
• Subtractive mode (−) — the percentage is subtracted (Zakat, discounts, depreciation)

Toggle between them with a single button on the main screen. The field labels update dynamically to match the current rate and direction.

Flexible terms: before, after, and amount

The terms Before, After, and Amount are deliberately generic so they work across many use cases:

• Tax/VAT: Taxable Amount → Total Amount → Tax Amount
• Commission: Base Price → Price Including Commission → Commission Amount
• Zakat: Zakatable Wealth → Remaining Wealth → Zakat Amount

For a full mapping across discount, markup, interest, insurance, payroll, and more, see the Terminology Reference.

Quick start

1. Open the calculator.
2. Set your flat rate (%)
3. Tap Before, After, or Amount to choose which value you know.
4. Enter the amount using the keypad.
5. The other two values appear instantly.

The rest of this manual explains every feature in detail.