Under 5 kg, Australia Post prices every domestic parcel on one ladder of five rungs — but what picks your rung changes with the packaging, and that difference is where the money is.
One ladder, two questions
XS S M L XL
$10.20 $11.70 $16.00 $20.25 $24.45
- In your own box, your weight picks the rung: up to 250 g is XS, 500 g is S, 1 kg is M, 3 kg is L, 5 kg is XL. The box itself is ignored — the same 750 g parcel costs $16.00 in a 10 cm box and in a 60 cm cube.
- In Australia Post's satchels, the size that fits picks the rung — and every satchel takes 5 kg, whatever its letter. XS is 21.5 × 28 cm, S 35.5 × 22.5, M 39 × 27, L 41.5 × 31.5, XL 51 × 44.
(Prices and sizes from Australia Post's July 2026 charges, posted in Melbourne — the current ones are on their postage calculator.)
The rule
Compare the satchel size your item actually fits against the rung its weight already pays, and take the lower.
- 750 g of nails. Weight says rung M — $16.00. They fit an XS satchel — $10.20. Two rungs down, $5.80 saved.
- 4 kg of the same nails. Weight says XL — $24.45. Still dense, still small, fits an S satchel, and a satchel takes 5 kg — $11.70. $12.75 saved, and the heavier the dense parcel, the wider the gap.
- A framed print, 30 × 30 × 2 cm, also 750 g. Weight says M — $16.00. Flat but wide, it fits nothing below XL — $24.45. Keep the box.
Dense and small wins. Big and light loses. That is the whole game.
Mind the letters
The same letters mean two different things: S is a 500-gram rung for your own box and a 5-kilogram satchel for theirs. When you compare, compare a weight against a size — never a letter against a letter.
Where it stops
- Above 5 kg there are no satchels, and the saving is gone.
- Prepaid satchels are the same ladder with the postage bought up front: $10.55 · $12.05 · $16.40 · $20.70 · $24.95. A parcel in one of those is already paid for — no shipping price applies to it at all.
What TellShip quotes today
TellShip prices your parcels as your own boxes. A parcel you actually ship in a satchel can therefore cost you less at the counter than what checkout charged — money you keep. There is no satchel setting in the app today; this page is the saving you can take by hand.