How to accurately calculate your parcel postage

First, look at where you’re sending

The first element that impacts the cost of postage is the origin and destination, which will determine which zone your delivery falls into.

If you’re a MyPost Business customer, your savings band will determine how much you could save.

Learn more about savings bands and charging zones (PDF 642kB).

Next, your packaging comes into play

Postage costs are also influenced by your choice of packaging. If you choose Australia Post’s flat rate packaging, it’s pretty straightforward. As long as the parcel weighs 5kg or less within Australia, then your postage is calculated based on the size of your packaging. There are four packaging sizes to choose from - small, medium, large or extra-large parcel.

If you’d prefer to use your own packaging, then we look at its weight and dimensions to determine how much space it will take up in our vehicles. The postage is based on the greater of either the physical or cubic weight.

Maths not your strongest suit? Don’t worry, you can enter the physical weight and dimensions within MyPost Business and we will calculate the chargeable weight and parcel cost for you.

Just remember, with your own packaging, accuracy is key to paying the correct postage amount. Measure each dimension carefully—watching out for any bulky or protruding parts—and check that the parcel fits within our size and weight guidelines.

Finally, are you adding extra features?

Adding speedy delivery? Or cover for loss or damage? What about signature on delivery? If you add these optional extras for domestic sending or international shipping then the postage cost will be adjusted at the payment stage.

What happens if you miscalculated your postage?

Here’s what happens if you’re using your own packaging and have underestimated the cost of postage.

Our parcel processing machines will automatically detect if the parcel’s weight and dimensions are different to what was declared and paid for on the label.

We’ll let you know if any items have underpaid postage and send you details on how to view and make the payment.

Don’t worry, your parcel will still be delivered but it just means there may be an extra invoice that you hadn’t accounted for.

Want to keep things simple?

If you want to keep things simple then flat rate packaging is the easiest way to go because you don’t have to measure a parcel that’s below 5kgs.

Our flat rate satchels are also designed to be reused a second time, which means your customers can use the same satchel (PDF 558kB) if they need to return an item.

Each satchel comes with a second adhesive strip to make re-sealing easy and user-friendly instructions on how to use the satchel a second time. It all helps you deliver a great returns experience.

Here’s a quick explainer on how our postage is calculated (PDF 378kB). Don’t forget, you can always use our postage calculator¹ to get an idea of postage costs.