Invoice Calculators
Quick math helpers for your invoices: work out late-fee interest on overdue payments, VAT/GST, payment due dates, and the next invoice number — every result computed in your browser.
Invoice Calculators
Quick helpers for late fees, VAT math, due dates, and sequential numbering — every result is computed locally in your browser, with no signup.
Late Fee Calculator
Calculate APR-based late fees on overdue invoices with simple or compound interest.
CalculatorVAT / GST Calculator
Add VAT to a net price or extract VAT from gross, with country presets verified against official sources.
CalculatorPayment Due Date Calculator
Net 7/15/30/45/60/90, EOM, and 2/10 Net 30 — get the exact due date instantly.
CalculatorInvoice Number Generator
Sequential, audit-friendly invoice numbers in any format (INV-2026-001, etc.).
How to Use the Calculators
Get an answer in seconds with these simple steps:
Pick a Calculator
Choose the tool you need: late fee, VAT/GST, payment due date, or invoice number.
Enter Your Figures
Type in the amount, rate, dates, or starting number the calculator asks for.
Get the Result Instantly
The answer is computed in your browser as you type — nothing is sent to a server.
Use It on Your Invoice
Copy the figure into your invoice, or head to the templates to create the document.
Works in any modern browser: Chrome, Firefox, Safari, Edge. Need to create the invoice itself? Browse our invoice templates.
Why Use Our Free Calculators?
Frequently Asked Questions
What is the difference between a calculator and an invoice generator?
A calculator takes a few numbers or dates and returns a single result, for example the late fee owed on an overdue invoice, the VAT on a price, or a due date. An invoice generator takes your full billing details and produces a finished PDF invoice. If you need to create an invoice document, use the Invoice Templates instead.
Do the calculators run on your servers?
No. The late fee, VAT/GST, due date, and invoice number tools run entirely in your browser using client-side JavaScript. The numbers you enter are not sent to a server or stored anywhere.
How is the late fee on an overdue invoice calculated?
The Late Fee Calculator applies an annual percentage rate (APR) to the outstanding amount over the number of days it is overdue, using either simple or compound interest. The exact lawful rate depends on your contract and jurisdiction, so always confirm the applicable statutory rate before charging interest.
Can the VAT / GST calculator both add and remove tax?
Yes. You can add VAT to a net (pre-tax) price, or extract the VAT already included in a gross (tax-inclusive) amount. It includes country presets verified against official tax-authority sources, plus a custom-rate option.
Which payment terms does the due date calculator support?
It handles common net terms (Net 7, 15, 30, 45, 60, 90), end-of-month (EOM), and early-payment discount terms such as 2/10 Net 30, returning the exact calendar due date from your invoice date.
Are these calculators free to use?
Yes. Every calculator on MyInvoiceTemplate is completely free with no signup, account, or credit card required, and there are no usage limits.
Legal Disclaimer: The calculators provided on MyInvoiceTemplate are for general business purposes and convenience only. They do not constitute professional accounting, tax, or legal advice. Statutory interest rates and VAT/GST rules vary by contract and jurisdiction and change over time, so please confirm the applicable figures with a certified accountant before relying on a result.
Ready to Create the Invoice?
Once you have your figures, build a finished PDF invoice for any type or industry — free and without signup.
Browse Invoice Templates