Zone 1 (Local / < 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)
Zone 9 (Territories/Freely Associated States)
function calculatePostage() {
// Get Inputs
var lbs = parseFloat(document.getElementById('weightLbs').value) || 0;
var oz = parseFloat(document.getElementById('weightOz').value) || 0;
var length = parseFloat(document.getElementById('dimLength').value) || 0;
var width = parseFloat(document.getElementById('dimWidth').value) || 0;
var height = parseFloat(document.getElementById('dimHeight').value) || 0;
var zone = parseInt(document.getElementById('zoneSelect').value);
var service = document.getElementById('serviceType').value;
// Basic validation
if ((lbs === 0 && oz === 0) && (length === 0)) {
alert("Please enter a valid weight or dimensions.");
return;
}
// Calculate actual weight in Pounds
var actualWeight = lbs + (oz / 16);
if (actualWeight 0) actualWeight = 0.0625; // Min 1 oz
// Calculate Dimensional Weight (DIM)
// USPS Divisor is 166 for domestic
var cubicSize = length * width * height;
var dimWeight = 0;
var dimApplied = false;
// Dim weight applies to Priority and Express if volume > 1 cubic foot (1728 in^3)
// It also applies to Ground Advantage if over certain size, but simplified here for Zones 1-9
if (cubicSize > 1728 && (service === 'priority' || service === 'express')) {
dimWeight = cubicSize / 166;
}
// Determine Chargeable Weight
var chargeableWeight = actualWeight;
// Priority/Express logic for Dim Weight
if (dimWeight > actualWeight) {
chargeableWeight = dimWeight;
dimApplied = true;
}
// Round up to nearest Pound for pricing (USPS standard for >1lb or Priority)
// Exception: First Class/Ground under 15.99oz uses ounces, but for this calculator we simplify to pound increments for Zones logic
// For accurate estimation, we ceil the weight.
var pricingWeight = Math.ceil(chargeableWeight);
// Special case: Ground Advantage under 1lb is priced by oz blocks (4, 8, 12, 15.99).
// To simplify implementation without a massive DB, we treat <1lb as 1lb tier base, adjusted slightly.
if (pricingWeight < 1) pricingWeight = 1;
// Pricing Logic (Simulated 2024 Approximation Matrix)
// These are NOT live API rates, but algorithmic approximations of the Zone/Weight curves.
var baseRate = 0;
var perLbRate = 0;
var discountPct = 0; // Commercial Base Pricing discount
if (service === 'ground') {
// Ground Advantage Logic
// Approx Base: $4.75 – $5.50 for 1lb.
baseRate = 4.50 + (zone * 0.30);
perLbRate = 0.60 + (zone * 0.45);
discountPct = 0.20; // ~20% savings online
// Adjust for heavier items
if (pricingWeight > 20) perLbRate *= 1.1;
} else if (service === 'priority') {
// Priority Mail Logic
// Higher base, steeper zone curve
baseRate = 8.70 + (zone * 0.65);
perLbRate = 0.90 + (zone * 1.10);
discountPct = 0.15; // ~15% savings online
} else if (service === 'express') {
// Priority Mail Express Logic
baseRate = 28.50 + (zone * 2.00);
perLbRate = 3.50 + (zone * 3.00);
discountPct = 0.13; // ~13% savings online
}
// Calculate Retail Price
// Formula: Base + ((Weight – 1) * PerLbRate)
// If weight is 1, just base.
var weightFactor = pricingWeight – 1;
if (weightFactor 1 cu. ft).";
document.getElementById('dimMsg').style.display = 'block';
} else {
document.getElementById('dimMsg').style.display = 'none';
}
document.getElementById('retailRate').innerHTML = "$" + estimatedRetail.toFixed(2);
document.getElementById('onlineRate').innerHTML = "$" + estimatedOnline.toFixed(2);
document.getElementById('totalSavings').innerHTML = "$" + savings.toFixed(2) + " (" + (discountPct*100).toFixed(0) + "%)";
document.getElementById('result').style.display = 'block';
}
How to Calculate USPS Postage Rates Online
Calculating shipping costs accurately is essential for e-commerce businesses and casual shippers alike. The USPS Online Rate Calculator helps you estimate the postage required for your package based on four critical factors: weight, dimensions, destination zone, and service class.
1. Weight and Dimensions
USPS pricing is heavily dependent on the "chargeable weight" of your package. For smaller packages, this is simply the actual weight measured on a scale. However, for large, lightweight boxes, USPS uses Dimensional (DIM) Weight.
If your package volume (Length x Width x Height) exceeds 1 cubic foot (1,728 cubic inches), USPS calculates a theoretical weight using the formula:
DIM Weight = (Length × Width × Height) / 166
You will be charged for whichever is greater: the actual scale weight or the calculated DIM weight. Our calculator automatically checks for this condition.
2. Understanding USPS Zones
USPS does not charge based on state lines, but rather on the distance between the origin and destination zip codes, measured in "Zones."
Zone 1: Within 50 miles (Local)
Zone 4: 301 to 600 miles
Zone 8: 1801 miles or more
Zone 9: Freely Associated States and territories
The higher the zone number, the more expensive the postage. Shipping a 5lb box to Zone 1 might cost $10, while the same box to Zone 8 could cost $25.
Retail vs. Commercial Pricing
One of the biggest advantages of purchasing postage online (via platforms like Stamps.com, Pirate Ship, or eBay labels) is access to Commercial Base Pricing. The calculator above compares the standard "Retail" rate (what you pay at the Post Office counter) with the "Online" rate.
Service Type
Retail (Counter)
Online (Commercial)
Typical Savings
Ground Advantage
Standard Rate
Discounted
Up to 20%
Priority Mail
Standard Rate
Discounted
Up to 15%
Express
Premium Rate
Discounted
Up to 13%
Which Service Should You Choose?
USPS Ground Advantage™: The most economical option for packages up to 70 lbs. Delivery typically takes 2-5 business days. It includes $100 insurance.
Priority Mail®: Faster delivery (1-3 business days) with free packaging supplies (flat rate boxes) available. It is often the best value for packages between 1-10 lbs traveling long distances.
Priority Mail Express®: The only money-back guarantee service offering overnight delivery to most U.S. locations. It is significantly more expensive but necessary for time-critical shipments.