How to Calculate Net 30 Due Date
Step-by-step how to calculate Net 30 due date, plus a free calculator.
How to calculate Net 30: take the invoice date, add 30 calendar days, and that is your due date — unless the contract says business days. Use the tool below to avoid month-length mistakes.
Market reference
| Metric | Range | Note |
|---|---|---|
| Step 1 | invoice date | start |
| Step 2 | +30 days | calendar |
| Step 3 | write on invoice | due date |
| Optional | business days | if contracted |
Interactive example — how to calculate net 30
- Due date
- Fri, Jul 31, 2026
- Days from invoice
- 30 days
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Frequently asked questions
How do you calculate Net 30 manually?
Add 30 days to the invoice date on a calendar.
What if the month has 31 days?
Still add 30 days — don't assume month-end equals Net 30.
Does Excel help?
Yes (=A1+30), or use this calculator for business-day options.