Commerce Commerce 1.x Developer Calculations
As mentioned in the taxes documentation, Commerce handles calculations primarily on the order item level, in particular the tax calculation.
Here you’ll find what the different numbers for each calculation means and how they interact.
Order Items
Most calculations happen on the order item.
Subtotal
The subtotal is simply calculated as the price per item, times the quantity. This is the base price for a row in the cart/order.
Shipping
If per-item shipping costs are added (which is not something currently exposed in the core), the shipping field on the item will sum those up.
Discount
The discount field sums up order item price adjustments.
Total Before Tax
The total_before_tax is a sum of the subtotal, the shipping and the discount fields, prior to the tax calculation taking place (see total excluding tax description, below)
Total Excluding Tax
The total_ex_tax contains the total price for the item excluding the calculated tax.
If commerce.tax_calculation is set to exclusive, this value will be the same as total_before_tax.
However if commerce.tax_calculation is set to inclusive, it will be lower because total_before_tax is based on prices including tax, while total_ex_tax has removed the tax portion.
Tax
The total tax based on summing up the tax for the item. The tax field may consist of different tax rates stacked on top of each other.
Total
The actual grand total for this item.
Order
On the order objects you’ll find totals and non-item-specific numbers.
Subtotal
Sum of the subtotal of all order items combined.
Shipping
Sum of the shipping of all order items combined, plus the fee for each order shipment (based on shipping method) combined.
Discount
Sum of the discount of all order items combined.
Transaction
The total transaction fee for the order. This is calculated by taking the fee column of all transactions that have a status of pending or completed.
Total Before Tax
The total_before_tax is a sum of the subtotal, the shipping and the discount fields for all items combined.
Total Excluding Tax
The total_ex_tax contains the total price excluding the calculated tax.
If commerce.tax_calculation is set to exclusive, this value will be the same as total_before_tax.
However if commerce.tax_calculation is set to inclusive, it will be lower because total_before_tax is based on prices including tax, while total_ex_tax has removed the tax portion.
Tax
The total tax as calculated, from all items combined. The tax calculation uses the total_before_tax column as value to calculate tax on.
The tax field may consist of different tax rates stacked on top of each other.
Total
The actual grand total for the order.
Total Due
The total amount of the order that is as of yet unpaid. This is based on the total, minus the total amount that was already paid. The amount that was already paid is calculated by summing up the amount for all transactions with a status of completed.