We charge based on both the volume (size) and weight of your items. When our pricing page displays a cost based on weight, there is also a maximum size associated with that fee.
Full details on how you are charged and our exact size allowances and weight bands can be found on our allowances page.
The heaviest single item we can accept is 70kg / 154lb, and the largest item is 350,000cm³ / 21,350in³ in volume.
It is normal for your order to show a heavier weight than you originally stated, as the final weight figure displayed will have been calculated considering the size of the item as well as the physical weight.