Invoice Calculator
Create and calculate invoice totals with line items, tax, discounts, and shipping. Enter values for instant results with step-by-step formulas.
Formula
Total = (Subtotal - Discount) + Tax | Tax = (Subtotal - Discount) x Tax Rate
The invoice total is calculated by summing all line items (qty x unit price) for the subtotal, subtracting any percentage discount, then adding sales tax on the discounted amount.
Worked Examples
Example 1: Freelance Web Design Invoice
Problem: 3 line items: Web Design ($2,500 x 1), Logo Design ($800 x 1), Content Writing ($150 x 5 pages). 10% discount, 8% tax.
Solution: Subtotal: $2,500 + $800 + $750 = $4,050\nDiscount (10%): -$405\nAfter discount: $3,645\nTax (8%): +$291.60\nTotal: $3,936.60
Result: Subtotal: $4,050 | Discount: -$405 | Tax: $291.60 | Total: $3,936.60
Frequently Asked Questions
What should an invoice include?
A professional invoice should include: your business name and contact info, client's name and contact info, unique invoice number, invoice date and payment due date, itemized list of products/services with quantities and unit prices, subtotal, any applicable discounts, tax amount and rate, total due, payment terms (Net 30, due on receipt, etc.), and accepted payment methods. For tax compliance, include your business tax ID and the client's if required.
How do you calculate sales tax on an invoice?
Sales tax is calculated on the subtotal after discounts. Formula: Tax = (Subtotal - Discount) x Tax Rate. For example, on a $1,000 subtotal with 10% discount: discounted amount = $900, then at 8% tax: $900 x 0.08 = $72 tax, total = $972. Tax rates vary by state/locality (0-10%+ in the US). Some services may be tax-exempt. Always check your local tax regulations.
Is my data stored or sent to a server?
No. All calculations run entirely in your browser using JavaScript. No data you enter is ever transmitted to any server or stored anywhere. Your inputs remain completely private.
Can I share or bookmark my calculation?
You can bookmark the calculator page in your browser. Many calculators also display a shareable result summary you can copy. The page URL stays the same so returning to it will bring you back to the same tool.
How do I interpret the result?
Results are displayed with a label and unit to help you understand the output. Many calculators include a short explanation or classification below the result (for example, a BMI category or risk level). Refer to the worked examples section on this page for real-world context.
Can I use Invoice Calculator on a mobile device?
Yes. All calculators on NovaCalculator are fully responsive and work on smartphones, tablets, and desktops. The layout adapts automatically to your screen size.