Same City / Local (Zone 1)
Same State / Regional (Zone 2)
Interstate – Metro (Zone 3)
Interstate – Regional/Remote (Zone 4)
Regular Parcel Post
Express Post
Own Packaging
Small Satchel (Prepaid)
Medium Satchel (Prepaid)
Large Satchel (Prepaid)
Extra Large Satchel (Prepaid)
Estimated Postage Costs
Chargeable Weight:–
Calculation Method:–
Base Rate:–
Zone Loading:–
Service Surcharge:–
$0.00
*Estimates are based on general 2024 domestic retail rates using cubic weight where applicable. Actual costs may vary at the post office based on precise postcodes.
function calculatePostage() {
// 1. Get Inputs
var weightInput = document.getElementById('apWeight').value;
var lengthInput = document.getElementById('apLength').value;
var widthInput = document.getElementById('apWidth').value;
var heightInput = document.getElementById('apHeight').value;
var destination = document.getElementById('apDestination').value;
var service = document.getElementById('apService').value;
var packaging = document.getElementById('apPackaging').value;
// 2. Validate Numbers
var weight = parseFloat(weightInput);
var length = parseFloat(lengthInput) || 0;
var width = parseFloat(widthInput) || 0;
var height = parseFloat(heightInput) || 0;
// Validation for Own Packaging
if (packaging === 'own') {
if (isNaN(weight) || weight <= 0) {
alert("Please enter a valid weight.");
return;
}
if ((isNaN(length) || length <= 0) || (isNaN(width) || width <= 0) || (isNaN(height) || height 4000 divisor for cm)
var volume = length * width * height;
var cubicWeight = volume / 4000;
// Chargeable weight is the greater of actual or cubic
finalChargeableWeight = Math.max(weight, cubicWeight);
method = (cubicWeight > weight) ? "Cubic Weight" : "Actual Weight";
// Base Rate logic based on Chargeable Weight Tiers (Approx Retail)
if (finalChargeableWeight <= 0.5) baseRate = 10.60;
else if (finalChargeableWeight <= 1.0) baseRate = 14.50;
else if (finalChargeableWeight <= 3.0) baseRate = 18.25;
else if (finalChargeableWeight 5kg
baseRate = 21.95 + ((finalChargeableWeight – 5) * 1.50); // $1.50 per addt kg base
}
// Zone Multipliers (Approximating distance costs)
// Zone 1: Local (1.0), Zone 2: State (1.1), Zone 3: Interstate Metro (1.25), Zone 4: Remote (1.5)
var zoneMultiplier = 1.0;
if (destination === '2') zoneMultiplier = 1.15;
if (destination === '3') zoneMultiplier = 1.35;
if (destination === '4') zoneMultiplier = 1.60;
var adjustedBase = baseRate * zoneMultiplier;
zoneCost = adjustedBase – baseRate;
// Service Upgrade
if (service === 'express') {
// Express is roughly 1.3x – 1.5x of standard
serviceCost = adjustedBase * 0.35;
}
totalCost = adjustedBase + serviceCost;
}
// 4. Update UI
document.getElementById('resWeight').innerText = (typeof finalChargeableWeight === 'number') ? finalChargeableWeight.toFixed(2) + " kg" : finalChargeableWeight;
document.getElementById('resMethod').innerText = method;
document.getElementById('resBase').innerText = "$" + baseRate.toFixed(2);
document.getElementById('resZone').innerText = "$" + zoneCost.toFixed(2);
document.getElementById('resSurcharge').innerText = "$" + serviceCost.toFixed(2);
document.getElementById('resTotal').innerText = "$" + totalCost.toFixed(2);
document.getElementById('apResult').style.display = 'block';
}
Understanding Australia Post Shipping Rates
Calculating the cost of sending a parcel within Australia can be complex due to the various factors Australia Post uses to determine pricing. Whether you are an eCommerce business owner or sending a gift to a relative, understanding how these rates are calculated can help you choose the most cost-effective option.
1. Cubic Weight vs. Actual Weight
One of the most critical concepts in logistics is "Cubic Weight" (also known as Volumetric Weight). Australia Post reserves the right to charge based on how much space a parcel takes up in their van or plane, rather than just how heavy it is.
The Rule: If your parcel is light but large (like a pillow or a large plastic toy), you will likely be charged for the Cubic Weight. If the parcel is small but dense (like a box of books), you will be charged for the Actual Weight. The calculator above automatically determines which weight is higher and applies the cost accordingly. The standard conversion factor used for domestic road freight is usually 250kg per cubic metre.
2. "If It Packs, It Posts" Flat Rates
For items weighing up to 5kg, Australia Post offers "If It Packs, It Posts" packaging options. These are prepaid satchels or boxes available in Small, Medium, Large, and Extra Large sizes. This is often the cheapest option for sending heavy, small items interstate because the price is fixed regardless of the distance, provided the item fits inside the packaging and weighs less than 5kg.
3. Factors Influencing Your Rate
Distance (Zones): Sending a parcel within the same city (Metro to Metro) is significantly cheaper than sending it Interstate or to a rural country location.
Service Speed: Express Post generally costs 30% to 50% more than Regular Parcel Post but offers next-business-day delivery guarantees within specific networks.
Packaging: Using your own packaging allows for custom sizing, but you lose the benefit of flat-rate national pricing unless you are on a specific business contract.
Extra Cover: Insurance (Extra Cover) for items valued over $100 is charged at an additional rate, usually a few dollars per $100 of value.
4. How to Measure Your Parcel
To ensure your quote is accurate, always measure the longest points of your package. If your package is slightly bulging, measure the bulge. Round up to the nearest centimetre to avoid underpayment fines. For weight, round up to the nearest 100 grams.