Magento: Shipping price based on weight

Question

I want to apply the following shipping rules in the magento:

1-5kg - £5.95
6-10kg - £7.95
11-100kg + £0.21p per kilo on top of the £7.95 price.

I am facing problem with applying 0.21p per kilo in the last rule. Please advise if this is possible in magento or if any 3rd party extension can do this?

Answer 1

You can create your own shipping method.
Here is a nice tutorial.

What you need to change is the collectRates method.
That's the one that calculates the prices.

It could look something like this:

public function collectRates(Mage_Shipping_Model_Rate_Request $request)
{
    // skip if not enabled
    if (!Mage::getStoreConfig('carriers/'.$this->_code.'/active')) {
        return false;
    }
    $weight = $request->getPackageWeight();
    //if weight is above 100 method is not aplicable
    if ($weight > 100) {
         return false;
    }
    /* @var Mage_Shipping_Model_Rate_Result $result */
    $result = Mage::getModel('shipping/rate_result');
    /* @var Mage_Shipping_Model_Rate_Result_Method $method */
    $method = Mage::getModel('shipping/rate_result_method');

    $method->setCarrier($this->_code);
    $method->setCarrierTitle('Carrier title here'); //can come from config

    // record method information
    $method->setMethod($this->_code);
    $method->setMethodTitle('Method title here'); //can come from config
    //calculate price based on weight

    if ($weight < 6) {
        $price = 5.95; //value can come from config
    }
    elseif ($weight < 11) {
        $price = 7.95; //value can come from config
    }
    else {
        $price = 7.95;//base price - value can come from config
        $overweight = ceil($weight - 11); //round up the weight difference
        $price += 0.21 * $overweight;//add 0.21 for each kg over 11. Value ca come from config
    }
    //add the price to the method
    $method->setPrice($price);

    // add this rate to the result
    $result->append($method);

    return $result;
}