Calculate the shipping costs based on the distance of your store address and the clients address.
You can choose to use a defined zip code for your store, or the store address that is set in the store config

NO MORE SUPPORT, FREE FOR USE
This extension might be outdated, I decided to offer it free for use, no support is given anymore

UPDATE
Because some changes by the google API if you already installed this extension, follow these steps to make it work again:
https://www.thomaslang.nl/opencart-calculate-shipping-distance/

New installations are not affected by this, since the extension has been updated.

Promises

• Quick support (response within 24 hours)
  
• Regular updates
  
• Any good suggestions will be added
  

Features

• Easy for stores and restaurant deliveries.
  
• Choose max distance for this option to be available
  
• Shows a map with a store location marker and client location marker
  
• Choose Metric or Imperial settings (km's or miles)
  
• Add a base shipping price
  
• Add a price per mile / kilometer
  
• Add a price per mile / kilometer for specific shoppingcart weights
  
• Add exception zipcodes (zipcodes near who will only need to pay the base shipping price)
  
• Add a free shipping range near your location (for instance within 20 km's free shipping)
  
• Optionaly subtract the free shipping range from the calculation, if the client is beyond the free range (if customer is 40km's and free shipping is within 20km's he will only pay 20km shipping)

Installation instructions

Updates
(March 14th 2018) Fix
Update backend request to google distance matrix, to include your API key and make it an https request (to prevent connection error)

(September 22nd 2017) Fix
fixed version 3.0 & 3.1, there was a bug not displaying the selected options for
"use store address" and " Subtract range from calculation"

(September 8th 2017) New in 3.1
Added feature to display the route between the store and shipping address points on the map, this is only useful for stores who don't ship overseas. (see extension images for clarification)

(July 3rd 2017) New in 3.0
- New version for opencart 3.0

(March 31st 2017) New in 2.7.1
- There was a bug in the admin view template of version 2.7 where weight rate had a tab in it's textarea, resulting in an error.

Older changelog details: http://www.thomaslang.nl/opencart-calculate-shipping-distance/