Letter (Standard Envelope)
Large Envelope (Flat)
Package / Parcel
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 (US Territories)
Distance is measured from origin zipcode.
Pounds
Ounces
Estimated Retail Postage
Understanding USPS Postage Rates in 2024
Calculating the correct postage for your mail is essential to ensure delivery and avoid returns. The United States Postal Service (USPS) determines rates based primarily on three factors: the shape of the mailpiece, the weight, and the distance it travels (Zones).
1. Mail Shapes and Limitations
The "Shape" of your mailpiece dictates which service class applies:
Letters: Standard envelopes. To qualify as a letter, it must be rectangular, at least 3.5 inches high by 5 inches long, and no more than 3.5 ounces in weight. If it is rigid, square, or has clasps, it may be subject to a "non-machinable" surcharge.
Large Envelopes (Flats): These must be flexible, uniformly thick, and rectangular. The maximum weight for a First-Class Flat is 13 ounces. If it exceeds this weight, it automatically bumps up to Priority Mail.
Packages (Parcels): Any mailpiece that is rigid, thick (over 3/4 inch), or exceeds the dimensions of a Large Envelope is considered a package. Since mid-2023, "USPS Ground Advantage" has replaced First-Class Package Service and Retail Ground as the standard economical option.
2. Weight Calculation
USPS rounds weight up. For letters and flats, postage is calculated based on ounces. For packages (Ground Advantage and Priority Mail), weight is generally rounded up to the nearest pound for zones 1-9, although Ground Advantage has specific tiers for lightweight packages (4 oz, 8 oz, 12 oz, and 15.99 oz).
3. Understanding Zones
For packages, the distance the package travels affects the price. USPS divides the US into 9 Zones relative to the origin zip code:
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 (e.g., Guam, Puerto Rico).
The further the zone, the higher the cost for Ground Advantage, Priority Mail, and Express services.
Priority Mail vs. Ground Advantage
Ground Advantage is the most cost-effective way to ship packages under 70 lbs with a delivery window of 2-5 business days. It includes $100 of insurance.
Priority Mail offers faster delivery (1-3 business days) and also includes insurance. Retail pricing for Priority Mail is determined by weight and zone, though "Flat Rate" boxes are available which allow you to ship up to 70 lbs for a fixed price regardless of destination.
function toggleWeightWarning() {
var type = document.getElementById('mailType').value;
var lbs = parseFloat(document.getElementById('weightLbs').value) || 0;
var msg = document.getElementById('errorMessage');
// Simple UI feedback logic
if (type === 'letter' && lbs > 0) {
msg.innerText = "Letters cannot exceed 3.5 oz. Heavy items must be sent as Large Envelopes or Packages.";
msg.style.display = 'block';
} else if (type === 'flat' && lbs >= 1) {
msg.innerText = "Large Envelopes cannot exceed 13 oz. Heavier items must be sent as Priority Mail or Ground Advantage.";
msg.style.display = 'block';
} else {
msg.style.display = 'none';
}
}
function calculateShipping() {
// 1. Get Inputs
var type = document.getElementById('mailType').value;
var lbs = parseFloat(document.getElementById('weightLbs').value);
var oz = parseFloat(document.getElementById('weightOz').value);
var zone = parseInt(document.getElementById('destZone').value);
var resultDiv = document.getElementById('resultsList');
var resultsArea = document.getElementById('resultsArea');
var errorMsg = document.getElementById('errorMessage');
// Validation
if (isNaN(lbs)) lbs = 0;
if (isNaN(oz)) oz = 0;
if (lbs === 0 && oz === 0) {
errorMsg.innerText = "Please enter a valid weight.";
errorMsg.style.display = 'block';
resultsArea.style.display = 'none';
return;
}
// Convert total weight to ounces for logic
var totalOz = (lbs * 16) + oz;
var totalLbsRounded = Math.ceil(totalOz / 16); // Round up to nearest lb for parcels
if (totalLbsRounded === 0 && totalOz > 0) totalLbsRounded = 1;
errorMsg.style.display = 'none';
resultsArea.style.display = 'block';
resultDiv.innerHTML = "";
var htmlOutput = "";
// 2024 Retail Rate Constants (Approximations)
var stampPrice = 0.73;
var extraOzPrice = 0.24;
var flatBasePrice = 1.50;
// LOGIC: LETTER
if (type === 'letter') {
if (totalOz > 3.5) {
htmlOutput += "
Error
Weight exceeds Letter limit (3.5 oz). Please select Large Envelope or Package.
";
} else {
// First ounce + (totalOz rounded up – 1) * extraOz
var calcOz = Math.ceil(totalOz);
var cost = stampPrice + ((calcOz – 1) * extraOzPrice);
htmlOutput += buildResultRow("First-Class Mail Letter", "1-5 Business Days", cost);
}
}
// LOGIC: FLAT (Large Envelope)
else if (type === 'flat') {
if (totalOz > 13) {
htmlOutput += "
Switch to Priority Mail
Weight exceeds Large Envelope limit (13 oz). See Package rates below.
";
// Fallthrough to calculate package rates as it must be upgraded
htmlOutput += calculatePackageRates(totalOz, totalLbsRounded, zone);
} else {
var calcOz = Math.ceil(totalOz);
var cost = flatBasePrice + ((calcOz – 1) * extraOzPrice);
htmlOutput += buildResultRow("First-Class Mail Large Envelope", "1-5 Business Days", cost);
}
}
// LOGIC: PARCEL (Ground Advantage & Priority)
else {
htmlOutput += calculatePackageRates(totalOz, totalLbsRounded, zone);
}
resultDiv.innerHTML = htmlOutput;
}
function calculatePackageRates(totalOz, roundedLbs, zone) {
var html = "";
// — GROUND ADVANTAGE CALCULATION (Retail Estimations 2024) —
var gaPrice = 0;
// Base Rates for Lightweight (<1lb)
// Structure: Base + (ZoneFactor)
// Approximations derived from Notice 123
if (totalOz <= 4) {
gaPrice = 5.00 + (zone * 0.15);
} else if (totalOz <= 8) {
gaPrice = 5.50 + (zone * 0.20);
} else if (totalOz <= 12) {
gaPrice = 6.15 + (zone * 0.25);
} else if (totalOz < 16) {
gaPrice = 7.60 + (zone * 0.35);
} else {
// Over 1 lb
// Formula approximation: Base $8.00 + ($1.50 * lbs) + (Zone * WeightMultiplier)
// This is a rough heuristic to approximate the matrix
var base = 7.50;
var weightCost = (roundedLbs * 0.60);
var zoneCost = (zone * 0.90) * (1 + (roundedLbs * 0.1));
gaPrice = base + weightCost + zoneCost;
}
html += buildResultRow("USPS Ground Advantage™", "2-5 Business Days, $100 Insurance", gaPrice);
// — PRIORITY MAIL CALCULATION (Retail Estimations 2024) —
// Priority is significantly more expensive for zones 5-9
var pmPrice = 0;
// Base approximation
// 1lb Zone 1: ~$9.25, 1lb Zone 8: ~$14.00
// 5lb Zone 1: ~$11.00, 5lb Zone 8: ~$30.00
var pmBase = 9.00;
var pmWeightFactor = roundedLbs * 1.1; // steeply increases with weight
var pmZoneFactor = (zone * 1.5) * (1 + (roundedLbs * 0.15)); // steeply increases with distance
pmPrice = pmBase + pmWeightFactor + pmZoneFactor – 2; // adjustment
if (pmPrice Medium Flat Rate Box ($18.40), suggest Flat Rate logic visually (optional, but requested simple result)
// We will just show the calculated weight based rate.
html += buildResultRow("Priority Mail®", "1-3 Business Days, $100 Insurance", pmPrice);
// — PRIORITY MAIL EXPRESS —
var pmePrice = 30.00 + (roundedLbs * 3.5) + (zone * 4.0);
html += buildResultRow("Priority Mail Express®", "Next-Day to 2-Day Guarantee", pmePrice);
return html;
}
function buildResultRow(service, details, price) {
return `