Weight-based shipping is a powerful method for calculating shipping costs, but sometimes it may not work as expected, especially when certain product categories behave differently. If your WooCommerce store correctly calculates shipping for one or three or more bags but fails when two bags are added—especially for a specific category—this guide will help you troubleshoot and fix the issue.
1. Check the Weight-Based Shipping Rules
The first step is to verify the rules configured in your weight-based shipping plugin or WooCommerce settings.
Steps to Check:
- Go to WooCommerce → Settings → Shipping → Shipping Zones and select the relevant shipping method.
- Ensure that weight-based rules are correctly configured, especially for the “Min Weight” and “Max Weight”settings.
- Check if the rule applies correctly to the problematic category. Some plugins allow shipping rules per category, which could be misconfigured.
- Look for any “cart conditions” that might be limiting calculations when exactly two products are added.
2. Test Different Weight Combinations
To isolate the issue, try adding:
✅ One product → Works
❌ Two products → Fails
✅ Three or more products → Works
If the issue only occurs at two items, the weight threshold may be set incorrectly.
- Try changing the weight values slightly and test again.
- Set up a test product with the same category and a different weight to see if the issue persists.
3. Verify Product Weights and Category Assignments
Since the issue happens only in a specific category, there might be:
- Duplicate categories with different settings (Check under Products → Categories).
- Incorrect product weights assigned (Check under Products → Edit Product → Shipping).
- Hidden settings overriding global weight rules (Some plugins allow per-product shipping overrides).
Steps to Fix:
- Edit the affected product and go to the Shipping tab under Product Data.
- Verify the weight assigned to the product.
- Compare it with a product from another category that works correctly.
4. Check for Plugin Conflicts
If the issue persists despite correct weight settings, another plugin may be interfering.
How to Test for Conflicts:
- Disable all other shipping-related plugins except the weight-based shipping plugin.
- Test if the issue persists.
- If it works fine, enable plugins one by one until you find the conflict.
Common conflicting plugins include:
- Custom Shipping Classes plugins
- Multi-Vendor or Marketplace plugins
- Cache plugins (if shipping calculations are cached)
5. Clear Cache & Refresh Shipping Rates
If your store uses a caching plugin, it may be causing outdated shipping calculations.
How to Clear Cache:
- If using a caching plugin (WP Rocket, W3 Total Cache), clear the cache and test again.
- If Cloudflare or server-side caching is enabled, purge the cache.
- Temporarily disable caching and test shipping calculations.
Additionally, force WooCommerce to recalculate shipping:
- WooCommerce → Status → Tools
- Click Clear Transients and Clear Shipping Cache
6. Check Debug Logs for Errors
WooCommerce has a built-in logging system that may show why shipping isn’t being applied properly.
How to Enable Debugging:
- Go to WooCommerce → Settings → Shipping → Debug Mode
- Enable debugging and try adding two products again.
- Check the logs in WooCommerce → Status → Logs for shipping errors.
Final Fixes & Workarounds
- If no clear issue is found, try removing the product from the category and adding it back.
- Create a new shipping class and assign it to the affected category.
- Use an alternative weight-based shipping plugin (e.g., Table Rate Shipping for WooCommerce).
If none of the above steps resolve the issue, reach out to the shipping plugin developer for support.
