Ship-By Date Calculator for USPS
You know when the package has to arrive. This tool tells you the latest day you can drop it off at USPS for each mail class, counted back from your deadline using the delivery standards USPS publishes for your two ZIP codes.
By Hamdi Saidani.
The day it must be delivered.
How the Ship-By Date Is Calculated
Ship-by date = arrive-by date minus the delivery days USPS allows for your ZIP pair.
Days are counted the way USPS's own delivery-date tool counts them:
- Sundays count as transit days except the Sunday right after a Saturday mailing (mail dropped off the day before a holiday may skip Sundays too),
- holidays never count,
- a result that lands on a Sunday or holiday moves to the next delivery day,
- and the drop-off day itself must be a day USPS accepts mail.
Official delivery days: The USPS Service Standards Directory gives the number of days for every pair of 3-digit ZIP Code areas and each main mail class except Priority Mail Express.
Priority Mail is 2 or 3 days depending on the pair; Ground Advantage runs 2 to 5 days in the lower 48, and packages of 1 lb or more to or from Alaska, Hawaii and the territories can take much longer, often 10 days or more.
Official zones: The zone shown comes from the USPS Domestic Zone Chart for most ZIP codes. It sets the price, not the delivery days.
Counting backwards: The tool steps back from your arrive-by date one day at a time until it finds the latest drop-off day whose forward delivery date still lands on or before your deadline.
Priority Mail Express: Priority Mail Express is not in the USPS service standards directory.
USPS gives its 1 to 3 day guaranteed date for each ZIP pair in its Service Commitments tool and when you buy the label, so this tool plans with one figure from that range (the note under the results gives it) and marks it as an estimate.
The same data powers the delivery time calculator, which answers the opposite question: if I ship on a given day, when does it arrive?
Which Service Buys You the Most Time?
The faster the service, the later you can ship. Roughly, for the same deadline:
Tips for Shipping to a Deadline
- Drop off before the last collection time shown on the blue box or at the counter; a package handed in later counts from the next day USPS accepts mail, and Saturday counts.
- Ship a day earlier than the date this tool shows when the delivery matters, because the standards are targets, not guarantees.
- Check the USPS holiday list around Thanksgiving and Christmas: holidays do not count as delivery days, and USPS asks customers to mail early in December.
- For a guaranteed date, choose Priority Mail Express and keep the receipt: if USPS misses the guaranteed time, you can ask for a postage refund 2 to 30 days after mailing, or 30 to 60 days if you also bought an extra service (not for items to or from Alaska and Hawaii).
- Print the label online the day before so the package only needs to be handed in on your ship-by date.
Frequently Asked Questions
What is a ship-by date?
The ship-by date is the last day you can hand a package to USPS and still have it arrive by the date you need.
This tool works it out backwards for each mail class: it takes the delivery days USPS publishes for your two ZIP codes and counts back from your arrive-by date the way USPS's own delivery-date tool counts.
Sundays count as transit days except the Sunday right after a Saturday mailing, mail dropped off the day before a holiday may skip Sundays too, holidays never count, and regular mail is not delivered on Sundays or holidays.
Where do the delivery days come from?
From the USPS Service Standards Directory, which lists the delivery days USPS allows for every pair of 3-digit ZIP Code areas and each main mail class except Priority Mail Express, plus USPS's list of slower 5-digit ZIP codes.
Results marked "USPS standard" use those figures. On a few Hawaii and Alaska routes, Priority Mail gets one or two days more for a Friday or Saturday drop-off, as USPS's own delivery-date tool does.
Priority Mail Express is not in the directory; USPS gives its guaranteed date for a ZIP pair in its Service Commitments tool and at purchase, so here it is shown with a planning figure from its 1-3 day range (the note under the results gives the number) and marked "Estimate".
The zone shown only sets the price.
Does the ship-by date include the day I drop the package off?
No. USPS starts counting from the day after acceptance, so drop the package off before your Post Office's last collection time on the date shown.
If you hand it in after the last collection, it counts as dropped off the next day USPS accepts mail, and Saturday counts.
Why does the tool say "Too late" for some services?
Because that service needs more delivery days than remain before your arrive-by date.
Pick a faster service, choose a later arrival date, or ask your Post Office about Priority Mail Express next-day delivery, which is available to many ZIP codes.
Is the ship-by date guaranteed?
Only Priority Mail Express carries a USPS money-back delivery guarantee.
For every other service the dates are the delivery standards USPS publishes, not a guarantee, so for anything important ship a day or two before the date shown.