Estimate postage costs for Ground Advantage, Priority Mail, and Flat Rate boxes.
My Own Box (Calculated by Weight/Zone)
Priority Mail Flat Rate Envelope
Priority Mail Small Flat Rate Box
Priority Mail Medium Flat Rate Box
Priority Mail Large Flat Rate Box
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 / Continental US)
Zone 9 (US Territories/Freely Associated States)
Compare All Services
USPS Ground Advantage™
Priority Mail®
Priority Mail Express®
Estimated Shipping Costs
* Rates are estimates based on 2024 retail pricing. Actual costs may vary based on dimensional weight, specific zip codes, and online commercial discounts (e.g., Pirate Ship, Stamps.com).
How to Calculate USPS Shipping Rates
Calculating the cost to ship a box with the United States Postal Service (USPS) involves three primary factors: package dimensions/weight, the distance the package travels (Zones), and the speed of delivery required. This calculator helps you estimate these costs for both "Flat Rate" options and "Calculated" shipping using your own packaging.
Understanding USPS Zones
USPS does not charge based on state lines but rather on "Zones." Zones are determined by the distance between the origin zip code and the destination zip code.
Zone 1: 1-50 miles
Zone 4: 301-600 miles
Zone 8: 1801 miles or more (often coast-to-coast)
The higher the zone number, the more expensive the postage, particularly for heavier items sent via Priority Mail or Ground Advantage.
Flat Rate vs. Calculated Rates
One of the most common decisions for shippers is choosing between Flat Rate boxes and using their own packaging.
Priority Mail Flat Rate
"If it fits, it ships." The price is fixed regardless of weight (up to 70 lbs) or destination zone. This is often the best deal for heavy items traveling long distances (e.g., Zone 7 or 8). However, for lightweight items traveling nearby, Flat Rate is often more expensive than standard rates.
If you use your own brown box, the rate is determined by weight and zone. USPS Ground Advantage (formerly First Class Package and Retail Ground) is typically the most economical option for packages under 1 lb or those where speed is not the primary concern. It usually delivers in 2-5 business days.
Dimensional Weight Rules
For large, lightweight boxes, USPS may apply "Dimensional Weight" (DIM weight) pricing. If a package is larger than one cubic foot (1,728 cubic inches), you may be charged for the space the box takes up in the truck rather than its actual weight. Our calculator provides a standard weight-based estimate, but always measure your box to ensure it isn't subject to these surcharges.
// Logic to toggle inputs based on package type
function toggleDimensions() {
var pkgType = document.getElementById('packageType').value;
var serviceGroup = document.getElementById('serviceGroup');
// If flat rate, service selection is irrelevant (it's always Priority)
// However, we keep the weight input active because Flat Rate has a 70lb limit logic check
if (pkgType !== 'own') {
serviceGroup.style.opacity = '0.5';
document.getElementById('serviceType').disabled = true;
} else {
serviceGroup.style.opacity = '1';
document.getElementById('serviceType').disabled = false;
}
}
function calculateShipping() {
// 1. Get Inputs
var pkgType = document.getElementById('packageType').value;
var destZone = parseInt(document.getElementById('destZone').value);
var lbs = parseFloat(document.getElementById('weightLbs').value) || 0;
var oz = parseFloat(document.getElementById('weightOz').value) || 0;
var servicePref = document.getElementById('serviceType').value;
// 2. Calculate Total Weight in Pounds
var totalWeight = lbs + (oz / 16);
// Validation
if (totalWeight 70) {
alert("USPS limit is 70 lbs. Please reduce weight.");
return;
}
var resultsHTML = "";
// 3. Logic based on Package Type
// — SCENARIO A: FLAT RATE —
if (pkgType !== 'own') {
var price = 0;
var name = "";
// Approximate Retail 2024 Rates
if (pkgType === 'flat_env') {
price = 9.85;
name = "Priority Mail Flat Rate Envelope";
} else if (pkgType === 'flat_small') {
price = 10.40;
name = "Priority Mail Small Flat Rate Box";
} else if (pkgType === 'flat_medium') {
price = 18.40;
name = "Priority Mail Medium Flat Rate Box";
} else if (pkgType === 'flat_large') {
price = 24.75;
name = "Priority Mail Large Flat Rate Box";
}
resultsHTML += `
${name}$${price.toFixed(2)}
Flat Rate includes tracking and insurance up to $100.
`;
}
// — SCENARIO B: OWN PACKAGING (CALCULATED) —
else {
// Define Base Rates and Multipliers (Approximation of 2024 Retail Matrix)
// Ground Advantage Logic
// Base ~ $5.00 for Zone 1 <4oz. Increases with weight and zone.
// Formula approximation: Base + (Weight * W_Factor) + (Zone * Z_Factor)
// Heavy penalty for higher zones.
var groundPrice = 0;
var priorityPrice = 0;
var expressPrice = 0;
// — GROUND ADVANTAGE MATH —
// Base starting price
var g_base = 5.00;
// Weight cost: First 1lb is cheap, heavier gets pricier
if (totalWeight < 1) {
g_base = 4.75 + (totalWeight * 2); // approximate for oz
} else {
g_base = 7.00 + ((totalWeight – 1) * 1.50);
}
// Zone Multiplier (Distance cost)
// Zones 1-4 are cheap, 5-8 scale up fast
var g_zoneFactor = 0;
if (destZone <= 2) g_zoneFactor = 1.05;
else if (destZone <= 4) g_zoneFactor = 1.25;
else if (destZone 1) {
p_base = 9.25 + ((totalWeight – 1) * 2.10);
}
// Zone Multiplier
var p_zoneFactor = 0;
if (destZone <= 2) p_zoneFactor = 1.0;
else if (destZone <= 4) p_zoneFactor = 1.3;
else if (destZone 0.5) {
e_base = 30.45 + ((totalWeight) * 5.50);
}
var e_zoneFactor = 1 + (destZone * 0.15); // Scales linearly but starts high
expressPrice = e_base * e_zoneFactor;
// GENERATE OUTPUT BASED ON SELECTION
// Ground
if (servicePref === 'all' || servicePref === 'ground') {
resultsHTML += `
USPS Ground Advantage™2-5 Business Days$${groundPrice.toFixed(2)}