Retail limit is 13 oz. Commercial limit is 15.99 oz.
— Select Zone —
Zone 1 (Local / Close)
Zone 2 (Short Distance)
Zone 3
Zone 4
Zone 5 (Mid Distance)
Zone 6
Zone 7
Zone 8 (Far Distance)
Zone 9 (US Territories)
Zone depends on distance from origin zip code.
Estimated Retail Postage Cost
$0.00
Rate based on Weight Tier: – oz
Service: USPS Ground Advantage (formerly First Class Package)
Complete Guide to USPS First Class Package Rates
Calculating shipping costs for lightweight items is essential for small business owners, eBay sellers, and individuals shipping gifts. The USPS First Class Package Rate Calculator helps you estimate the postage required for parcels weighing less than a pound.
Note: As of mid-2023, USPS has merged First Class Package Service into USPS Ground Advantage. While the name has changed, the cost-effective structure for lightweight packages remains similar. This calculator uses the Ground Advantage retail pricing logic.
How Calculation Works
Postage rates for lightweight packages are determined by two main factors:
Weight (Ounces): Rates are tiered. Prices generally jump at 4 oz, 8 oz, and 12 oz increments.
Zone (Distance): The US is divided into zones (1-9) based on the distance from the sender's zip code to the recipient's zip code. Zone 1 is local, while Zone 8 is across the country.
Retail vs. Commercial Limits
One of the most confusing aspects of First Class/Ground Advantage shipping is the weight limit difference between Retail (Post Office counter) and Commercial (Online shipping software).
Service Type
Weight Limit
Where to Buy
Retail
Up to 13 oz
Post Office Counter
Commercial Base
Up to 15.999 oz
Pirate Ship, eBay, Stamps.com
If your package weighs between 13.1 oz and 15.999 oz, you must purchase postage online to get the First Class/Ground Advantage rate. If you go to the counter, they will charge you for Priority Mail, which is significantly more expensive.
Understanding Zones
The "Zone" is not a fixed geographic location like a time zone; it is a measurement of distance from your zip code.
Zone 1: 1-50 miles
Zone 2: 51-150 miles
Zone 3: 151-300 miles
Zone 4: 301-600 miles
Zone 5: 601-1000 miles
Zone 6: 1001-1400 miles
Zone 7: 1401-1800 miles
Zone 8: 1801+ miles
Tips for Lowering Shipping Costs
To maximize your savings when shipping small packages:
Use a Scale: Guessing weight can lead to returned packages or overpaying. A simple kitchen scale works well.
Round Up: USPS requires you to round up to the nearest ounce. If a package is 4.1 oz, you must pay the 5 oz (or next tier) rate.
Print Online: Commercial rates are typically 20-40% cheaper than retail counter rates.
function calculatePostage() {
// Elements
var weightInput = document.getElementById('packageWeight');
var zoneInput = document.getElementById('shippingZone');
var resultDisplay = document.getElementById('resultDisplay');
var costValue = document.getElementById('costValue');
var weightTierDisplay = document.getElementById('weightTierDisplay');
var errorDisplay = document.getElementById('errorDisplay');
// Reset
resultDisplay.style.display = 'none';
errorDisplay.style.display = 'none';
// Get Values
var weight = parseFloat(weightInput.value);
var zone = parseInt(zoneInput.value);
// Validation
if (isNaN(weight) || weight 13) {
errorDisplay.innerHTML = "Weight Exceeded: Retail First Class/Ground Advantage is limited to 13 oz.For packages over 13 oz at the retail counter, you must use Priority Mail.";
errorDisplay.style.display = 'block';
return;
}
// Determine Weight Tier (USPS usually groups 1-4, 5-8, 9-12, 13)
// Note: Prices below are representative estimates for Ground Advantage Retail as of late 2023/2024
// Logic: Use a base rate per tier + zone multiplier approximation
var baseRate = 0;
var tierLabel = "";
// Simplified Pricing Matrix (Approximation for Retail Ground Advantage)
// Structure: [Zone 1&2, Zone 3, Zone 4, Zone 5, Zone 6, Zone 7, Zone 8, Zone 9]
// Indices correspond to Zone – 1 (mapped logically below)
var rates = {
tier1: [5.40, 5.50, 5.60, 5.70, 5.80, 5.95, 6.10, 6.10], // 1-4 oz
tier2: [6.15, 6.25, 6.35, 6.45, 6.55, 6.70, 6.90, 6.90], // 5-8 oz
tier3: [6.90, 7.00, 7.15, 7.25, 7.40, 7.60, 7.80, 7.80], // 9-12 oz
tier4: [8.05, 8.20, 8.35, 8.50, 8.70, 8.90, 9.15, 9.15] // 13 oz
};
var selectedRateArr = [];
if (weight <= 4) {
selectedRateArr = rates.tier1;
tierLabel = "1 – 4";
} else if (weight <= 8) {
selectedRateArr = rates.tier2;
tierLabel = "5 – 8";
} else if (weight <= 12) {
selectedRateArr = rates.tier3;
tierLabel = "9 – 12";
} else {
selectedRateArr = rates.tier4;
tierLabel = "13";
}
// Map Zone Input (1-9) to Array Index (0-7)
// Zones 1 and 2 usually share the same cheapest rate
var zoneIndex = 0;
if (zone === 1 || zone === 2) zoneIndex = 0;
else if (zone === 3) zoneIndex = 1;
else if (zone === 4) zoneIndex = 2;
else if (zone === 5) zoneIndex = 3;
else if (zone === 6) zoneIndex = 4;
else if (zone === 7) zoneIndex = 5;
else if (zone === 8) zoneIndex = 6;
else if (zone === 9) zoneIndex = 7;
var finalCost = selectedRateArr[zoneIndex];
// Output
costValue.innerText = "$" + finalCost.toFixed(2);
weightTierDisplay.innerText = tierLabel;
resultDisplay.style.display = 'block';
}