Free Invoice Calculator
Add line items, set sales tax, apply a discount, and get the invoice total instantly. Built for freelancers, small business owners, and service providers.
- Line subtotal
- $0.00
- Invoice total
- $0.00
- Balance due
- $0.00
How this is calculated
The calculator uses the standard US invoicing convention: discount is applied first, then sales tax is applied to the discounted amount, then shipping/fees are added after tax. Amount already paid is subtracted last to give the balance due.
1.Line subtotal
sum( quantity × unit price )
Each line is multiplied independently, then summed.
2.Discount amount
discount $ — or — line subtotal × (discount % / 100)
A discount that exceeds the line subtotal is clamped to the subtotal so the taxable amount is never negative.
3.Taxable amount
line subtotal − discount amount
4.Sales tax
taxable amount × (tax % / 100)
Tax is applied to the discounted subtotal, not to the original line subtotal. This is the convention most US invoicing software uses.
5.Invoice total
taxable amount + sales tax + shipping/fees
Shipping and fees are added after tax, not taxed themselves. Some states require sales tax on shipping — adjust the tax line if your state does.
6.Balance due
max(0, invoice total − amount paid)
If the client overpaid you have a credit memo situation, which is out of scope here — the calculator caps balance due at $0.
For reference only. Verify your state's sales tax rules with your Department of Revenue — services are taxed differently from goods in many states, and shipping taxability varies.
How to use the invoice calculator
- Describe each line item. Use a short, specific description that the client can match to the work or product they ordered. “Logo design — primary lockup” is better than “Design work.”
- Enter quantity and unit price. For service work, quantity is often hours and unit price is your hourly rate. For products, quantity is units sold and unit price is the per-unit cost.
- Add your sales tax rate. Use the percentage applicable in your jurisdiction. If you're unsure, leave this at 0 and check with your state Department of Revenue.
- Apply discounts if any. Toggle between flat amount and percentage. The discount applies before tax.
- Use the total in your formal invoice. The calculator does the math; the invoice itself still needs your business name, client details, due date, payment terms, and accepted payment methods. That's what the editable template handles.
Example: freelance designer billing 12 hours plus revisions
A freelance designer wraps up a brand identity project. Their invoice has three lines:
- Brand strategy & competitive audit — 1 × $1,200 = $1,200
- Logo system — primary + secondary lockups — 1 × $2,400 = $2,400
- Stakeholder presentation revisions — 4 hours × $175 = $700
Subtotal: $4,300. Their state taxes services at 6.625%. With no discount, sales tax adds $284.86 and the total due is $4,584.86. That total goes on the formal invoice they send the client.
What the calculator does not do
This is math, not a complete invoice. To bill an actual client you still need a structured invoice document with:
- Your legal business name, address, and contact info
- The client's legal entity name and billing address
- A unique sequential invoice number
- Issue date and explicit calendar due date
- Payment terms (Net 15, Net 30, etc.) and late-fee policy
- Accepted payment methods with instructions
- A signature or acceptance line
All of these are in the Professional Invoice Template Pack — fillable PDF and editable Word formats, plus a 30-row invoice tracker, payment receipt, late-payment reminder, and client information sheet.
Want the editable version?
Professional Invoice Template Pack
Complete invoicing toolkit with tracker, payment receipts, and late-payment letters
Related resources
- What to include on a formal invoice (guide)
- Free vs paid invoice templates: which fits your business
- Invoice template: Word vs Excel
- Professional Invoice Template Pack
- All business forms