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
Late fees and interest on overdue invoices: an annual rate (simple or compounded daily), % per month, % per day, a one-time % or a flat fee, with legal default rates for 50 states + DC.
CalculatorVAT / GST Calculator
Add VAT to a net price or extract VAT from gross, with country presets verified against official sources.
CalculatorReverse VAT Calculator
Take VAT out of a VAT-inclusive (gross) price: the net price and the VAT it contains, for any rate.
CalculatorReverse Charge VAT Calculator
VAT to self-account, VAT to deduct and your net cost under the reverse charge, with EU and UK invoice wording.
CalculatorUK VAT Deadline Calculator
VAT return and payment due dates for the standard scheme, Annual Accounting and payments on account, with Direct Debit, CHAPS and Bacs timing.
CalculatorInvoice Due Date Calculator
Invoice date + payment term = due date and weekday: Net terms, EOM (both methods), prox, 2/10 Net 30, and days between two dates.
CalculatorBilling Cycle Calculator
Every billing date of a 7, 14, 28 or 30-day, monthly, quarterly or yearly cycle, with each invoice's due date.
CalculatorInvoice Calculator
Add line items, a discount, tax, shipping and a deposit; see the formula with your numbers.
CalculatorInvoice Number Generator
The next sequential invoice number or a numbered list, in formats like INV-2026-001.
GeneratorRandom Invoice Number Generator
Random, non-sequential invoice-style IDs (4–16 characters, up to 100 at a time), generated in your browser. For VAT/GST invoices use a sequential series.
GeneratorPO Number Generator
Next PO number or a numbered batch for your PO log, with an optional department or project code.
Letter toolDemand Letter Generator
A formal demand for payment with the interest computed and, if no rate was agreed, your state's statute cited.
CalculatorEarly Payment Discount
What 2/10 Net 30 is really worth, annualized — for the buyer and the seller.
CalculatorDSO Calculator
Days Sales Outstanding from your receivables and credit sales — and what a faster cycle frees up.
CalculatorInvoice Aging Calculator
Paste your open invoices, get an aging report by bucket (current, 1–30, 31–60, 61–90, 90+).
ConverterAmount to Words
Invoice totals written out in words — international (million/billion) or Indian (lakh/crore) numbering.
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.
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?
Comparing free invoice tools? What "free" means: invoice generator limits compared.
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 in your browser, and the amounts you enter are not sent to a server or saved. The one exception is the late-fee calculator's demand-letter link, which carries the amount, rate and due date in its web address (URL).
How is the late fee on an overdue invoice calculated?
The Late Fee Calculator applies an annual interest rate to the outstanding amount over the number of days it is overdue, as simple or daily-compounded interest, or works out a fee set as a percentage per month, a percentage per day, a one-time percentage or a flat amount. 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. The calculators run entirely in your browser and are not metered; the site's fair-use cap (20 PDFs per device per day) applies only to PDF generation, not to calculators.
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