It requires your store to use US Dollars as its currency and your server to have SimpleXML installed. The extension primarily works with measurements in Inches (in) and weight in Pounds (lbs), but other units can be converted automatically.
USPS requires a base country of the United States, Puerto Rico or US Virgin Islands and can calculate domestic and international parcel rates.
Installation ↑ Back to top
To install this extension, you can follow these instructions, or use the below steps to do a manual installation.
- Download the extension from your dashboard
- Upload the plugin folder to your /wp-content/plugins/ directory
- Activate ‘WooCommerce USPS’ from the Plugins menu within WordPress
More information at: .
API & Debug
Go to: WooCommerce > Settings > Shipping > USPS.
- USPS User ID – You can use our USPS User ID (this is set automatically) or get your own by signing up for a Webtools account on USPS.com.
- Debug Mode – Enable debug mode to show debugging info on your cart/checkout. This information is shown to ALL users, so you can test when logged out.
Setup and Configuration ↑ Back to top
- Go to: WooCommerce > Settings > Shipping.
- Select the Shipping Zone you want to add the method to, and click the Add shipping method + button on the right
- Select USPS from the dropdown and press Add shipping method:
- Configure the settings:
- Method Title – Name the shipping method. This is visible to customers.
- Offer Rates – Choose the options you want to give customers.
- Fallback – Enter a fallback shipping cost (optional), if no rates are returned from the API. This allows the customer to check out if USPS does not return matching rates. When using this option, do not use a dollar sign, just enter the amount (ex: 12.50).
- Flat Rates
- Flat Rate Boxes and Envelopes – Enable this option to offer shipping using USPS Flat Rate services. Items are packed into the boxes/envelopes, and the customer is offered a single rate.
- Express Flat Rate Title – Give a custom name to the express flat rate.
- Priority Flat Rate Title – Give a custom name to the priority flat rate.
- Additional Fee – Enter a fee per box excluding tax, such as an amount (2.50) or a percentage (5%). Or leave blank to disable.
- API Rates – Check to enable non-flat rates using the USPS API. Default is all services available; or choose what to offer from the available shipping services listed below. You can adjust:
- Enable API Rates – This enables non-flat rate services.
- Origin Postcode – Postcode from where you ship. It is sent to the USPS API.
- Shipping Rates – Retail rates are standard costs, Commercial rates are discounted.
- Parcel Packing Method – See below for more detailed explanation.
Available Shipping Services ↑ Back to top
These services are included with the USPS Shipping extension:
- First-Class Mail® Parcel
- First-Class Mail® Large Envelope
- First-Class Mail® Postcards
- First-Class Mail® Stamped Letter
- First-Class™ Postcard Stamped
- First-Class™ Large Postcards
- First-Class™ Keys and IDs
- First-Class™ Package Service
- First-Class Mail® Metered Letter
- First-Class™ Package Service Hold For Pickup
- Priority Mail Express™ Hold for Pickup
- Priority Mail Express™
- Priority Mail Express™ Sunday/Holiday
- Retail Ground™
- Media Mail®
- Library Mail
- Priority Mail®
- Priority Mail® Keys and IDs
- Priority Mail® Hold For Pickup
- Priority Mail® Regional Rate Box A
- Priority Mail® Regional Rate Box B
- Priority Mail Express International™
- Priority Mail International®
- Global Express Guaranteed® (GXG)
- Global Express Guaranteed® Document
- Global Express Guaranteed® Non-Document Rectangular
- Global Express Guaranteed® Non-Document Non-Rectangular
- USPS GXG™ Envelope
- First Class Mail® International Letters
- First Class Mail® International Large Envelope
- First Class Package International Service™
- International Postcards
Flat Rate Shipping Options
- Priority Mail Flat Rate™ – Envelopes (Legal, Letter, Gift Card, Padded, Small, Window) and Boxes (Small, Medium 1 and 2, Large, APO/DPO/FPO Large, Large Board Game, Prepaid Forever® Packaging)
- Priority Mail Express Flat Rate™ – Envelopes (Envelope, Legal, Padded) and Boxes (Top-Loading, Side-Loading)
- Priority Mail International Flat Rate® – Envelopes (Legal, Letter, Gift Card, Padded, Small, Window) and Boxes (Small, Medium 1 and 2, Large, APO/DPO/FPO Large, Large Board Game)
To enable any of these options:
Select the Standard Services option to ‘Enable Standard Services from the API’.
You also have the option to rename the service and include a negative/positive price adjustment by the default currency or a percentage.
- Price adjustments ($) – Add a flat adjustment to the USPS service.
- Price adjustments (%) – Add a percentage adjustment to the USPS service.
Flat Rate Services ↑ Back to top
If enabled, the flat rate box option creates a single quote based on USPS Flat Rate Services. To do this, the system uses the box packer (explained below) applying USPS box dimensions. Packed boxes are then combined to offer a single rate (named by your ‘method title’).
It is important to note that Flat Rate Shipping prices come directly from USPS, and you cannot add or modify pricing for this option.
Parcel Packing Method ↑ Back to top
There are three packing methods with USPS, and each affects the parcels you send to the API.
Per-Item ↑ Back to top
Each item in your cart (non-virtual) is sent to the USPS API. Quotes for all items are combined to calculate the final cost.
Pack into boxes ↑ Back to top
Items are packed into pre-defined boxes and sent to the API. We recommend this option. See Box Packing below for more information.
Weight based ↑ Back to top
Regular sized items (< 12 inches) are grouped and quoted for weights only. Large items are quoted individually.
The box packer included with this shipping method lets you group items into packages for which you define height, width, length, weight and max-weight. Packing is mainly volume based but also considers item size.
Setting up box sizes ↑ Back to top
When using the ‘Recommended: Pack into boxes with weights and dimensions’ Parcel Packing Method, the Box Sizes table will appear. Click ‘Add Box’ to set up dimensions for your packages.
Name: This allows you to name your custom packages. This name will show in the Debug if that package is used.
L (in), W (in), H (in): The first set of dimensions are the outer dimensions of the package. These are the dimensions passed to the API. If you are working with a flat rate box via the API (i.e., Regional Boxes), use the API’s ‘inner dimensions’ for your box’s outer dimensions. Your box must ‘fit’ inside.
Inner L (in), Inner W (in), Inner H (in): The second set of dimensions are for the inner dimensions of the packaging. This should be the outer dimensions minus the thickness of the package walls. These dimensions are used for packing and items must fit within them (they cannot be the same size as the products, allow for a little extra room).
Weight of Box (lbs): This is the weight of the empty box by itself. This weight is added to the total weight of the contents.
Max Weight (lbs): This is the maximum weight your box can hold. This includes the weight of the box and the contents.
Letter: This checkbox determines whether your package is a letter (envelope) or a box.
How the calculation works ↑ Back to top
The box packer:
- Finds boxes that fit items being packed (uses H x W x D).
- Packs all items into boxes (using volume).
- Uses the largest box fitting 100% of items *or* uses the highest % packed box, and then passes unpacked items back (and repeats the process)
- Packs unpackable items alone, using item dimensions.
- Returns all packed boxes.
Media Mail® ↑ Back to top
To enable Media Mail®, you must select the ‘Enable Standard Services from the API’ option. You then have two options: a) You can do nothing, which allows any item to use Media Mail®; or b) if only some of your products are eligible for Media Mail®, you need to give each product a shipping class and restrict Media Mail® to use only that class or classes.
After setting up shipping classes, you can restrict settings in your Shipping Zone USPS rate:
Customer Usage ↑ Back to top
Customers can get quotes based on the address entered from two places:
- Cart page – by using the shipping calculator
- Checkout page – by filling in shipping and billing forms
Troubleshooting ↑ Back to top
No rates returned/no rates available ↑ Back to top
- Enable debug mode to see debugging info on the cart page. This often reveal the issue.
- Check that products have sizes and weights set – without this, the calculation cannot be performed.
- Go to: WooCommerce > Settings > General and check that your store’s base country is the United States and US Dollars is the currency.
- Check that the plugin is linked to USPS API. It uses wp_remote_post, which makes use of fsockopen/CURL.
If you need help with adding weights/dimensions, see:
“UserName exceeds maximum length of 12 characters” error message ↑ Back to top
If you receive this error message when the debug mode is enabled, you need to use a shorter username.
Customize ↑ Back to top
Filter Flat Rate Services ↑ Back to top
To change the USPS package to envelope so dimensions are fixed, add this to your theme’s functions.php file:
To remove all the USPS Priority Flat Rate envelopes, leaving only the Small, Medium, and Large Flat Rate boxes, add this to your theme’s functions.php file:
The codes for each flat rate box can be found below:
Priority Mail Express
Priority Mail Express Flat Rate Envelope: d13
Priority Mail Express Legal Flat Rate Envelope: d30
Priority Mail Express Padded Flat Rate Envelope: d63
Priority Mail Flat Rate Envelope: d16
Priority Mail Flat Rate Medium Box (Side Loading): d17
Priority Mail Flat Rate Medium Box (Top Loading): d17b
Priority Mail Flat Rate Large Box: d22
Priority Mail Flat Rate Large Box (Board Game): d22a
Priority Mail Flat Rate Small Box: d28
Priority Mail Padded Flat Rate Envelope: d29
Priority Mail Gift Card Flat Rate Envelope: d38
Priority Mail Window Flat Rate Envelope: d40
Priority Mail Small Flat Rate Envelope: d42
Priority Mail Legal Flat Rate Envelope: d44
International Priority Mail Express
Priority Mail Express Flat Rate Envelope: i13
Priority Mail Express Legal Flat Rate Envelope: i30
Priority Mail Express Padded Flat Rate Envelope: i63
International Priority Mail
Priority Mail Flat Rate Envelope: i8
Priority Mail Padded Flat Rate Envelope: i29
Priority Mail Flat Rate Small Box: i16
Priority Mail Flat Rate Medium Box (Side Loading): i9
Priority Mail Flat Rate Medium Box (Top Loading): i9b
Priority Mail Flat Rate Large Box (Top Loading): i11
Exclude a country from USPS rates ↑ Back to top
If you wish to exclude a country from receiving USPS rates, the easiest way is to use Shipping Zones (WooCommerce 2.6+). However if you wish, you can use the snippet below. Change US to the country code you’d like to exclude:
FAQ ↑ Back to top
Does Shipping Zones work with USPS Shipping? ↑ Back to top
How can I get First Class Mail® International Large Envelope rates to display?
You need to use the Recommended parcel packing method and ensure that the Letter checkbox is ticked:
Questions and Feedback ↑ Back to top
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