Standard Letter (1oz – 3.5oz)
Large Envelope / Flat (1oz – 13oz)
Postcard
Package / Ground Advantage (up to 15.99oz)
Standard letters must be rectangular and uniform thickness.
Zone 1 (Local/Close)
Zone 2
Zone 3
Zone 4
Zone 5
Zone 6
Zone 7
Zone 8 (Far)
Zone 9 (Territories)
Distance based. Zone 1 is closest, Zone 9 is furthest.
Mail Class:First Class Letter
Weight Class:1 oz
Zone:N/A
Estimated Retail Price:$0.00
*Rates are based on standard USPS Retail pricing. Commercial rates may be lower.
function toggleZoneField() {
var type = document.getElementById("mailType").value;
var zoneGroup = document.getElementById("zoneGroup");
var helper = document.getElementById("typeHelper");
if (type === "package") {
zoneGroup.style.display = "block";
helper.innerHTML = "Formerly 'First Class Package'. Now part of USPS Ground Advantage.";
} else {
zoneGroup.style.display = "none";
if (type === "letter") helper.innerHTML = "Standard letters must be rectangular and uniform thickness.";
if (type === "flat") helper.innerHTML = "Large envelopes must be flexible and uniformly thick.";
if (type === "postcard") helper.innerHTML = "Rectangular, at least 3.5 x 5 inches.";
}
}
function calculatePostage() {
var type = document.getElementById("mailType").value;
var weightRaw = document.getElementById("weightInput").value;
var weight = parseFloat(weightRaw);
var zone = parseInt(document.getElementById("zoneSelect").value);
var price = 0;
var className = "";
var displayWeight = "";
var displayZone = "N/A";
var errorMsg = "";
// Basic Validation
if (isNaN(weight) || weight 0 && weight > 1) { // Technical max is negligible, but essentially 1oz card stock
// Assuming standard postcard
}
}
else if (type === "letter") {
className = "First-Class Mail Letter";
if (weight > 3.5) {
// Determine if we should upgrade to flat
className = "Overweight Letter (Rated as Large Envelope)";
// Switch logic to flat
type = "flat";
} else {
// Base $0.73 for 1oz + $0.24 per additional oz
var priceBase = 0.73;
var priceExtra = 0.24;
var chargeableWeight = Math.ceil(weight); // USPS rounds up to next oz
price = priceBase + ((chargeableWeight – 1) * priceExtra);
displayWeight = chargeableWeight + " oz";
}
}
if (type === "flat") {
className = "First-Class Mail Large Envelope (Flat)";
if (weight > 13) {
className = "Overweight Flat (Rated as Package)";
type = "package"; // Upgrade to package logic
} else {
// Base $1.50 for 1oz + $0.24 per additional oz
var priceBase = 1.50;
var priceExtra = 0.24;
var chargeableWeight = Math.ceil(weight);
price = priceBase + ((chargeableWeight – 1) * priceExtra);
displayWeight = chargeableWeight + " oz";
}
}
if (type === "package") {
// USPS Ground Advantage Retail (Formerly First Class Package Service)
// Weight tiers: 4, 8, 12, 15.99
// Zones 1-9
className = "USPS Ground Advantage Retail (Package)";
displayZone = "Zone " + zone;
if (weight > 15.99) {
alert("First Class / Ground Advantage Retail (Light) is limited to 15.99 oz. Please consult Priority Mail rates for heavier items.");
return;
}
var chargeableWeight = weight; // Use raw for logic, though tiering handles it
var tierIndex = 0; // 0=4oz, 1=8oz, 2=12oz, 3=15.99oz
if (weight <= 4) tierIndex = 0;
else if (weight <= 8) tierIndex = 1;
else if (weight <= 12) tierIndex = 2;
else tierIndex = 3;
// Simplified Retail Matrix (Approximate 2024 Retail Rates)
// Rows: Tiers [4oz, 8oz, 12oz, 16oz]
// Cols: Zones [1&2, 3, 4, 5, 6, 7, 8, 9]
// Note: Arrays use index 0 for Zone 1/2, index 1 for Zone 3… index 7 for Zone 9.
var rates = [
// 4 oz
[5.00, 5.10, 5.15, 5.25, 5.35, 5.50, 5.65, 5.65],
// 8 oz
[5.75, 5.85, 5.90, 6.00, 6.10, 6.25, 6.45, 6.45],
// 12 oz
[6.50, 6.60, 6.65, 6.75, 6.90, 7.15, 7.35, 7.35],
// 15.99 oz
[7.25, 7.40, 7.55, 7.75, 8.00, 8.35, 8.60, 8.60]
];
// Map zone input (1-9) to array index
// Zone 1 & 2 share index 0
var zoneIndex = 0;
if (zone index 1, Zone 9 -> index 7
if (zoneIndex > 7) zoneIndex = 7; // Cap at Zone 9
price = rates[tierIndex][zoneIndex];
var tierLabel = [4, 8, 12, 16];
displayWeight = "Up to " + tierLabel[tierIndex] + " oz";
}
// Output Result
document.getElementById("resClass").innerHTML = className;
document.getElementById("resWeight").innerHTML = displayWeight;
document.getElementById("resZone").innerHTML = displayZone;
document.getElementById("resPrice").innerHTML = "$" + price.toFixed(2);
document.getElementById("result").style.display = "block";
}
Understanding USPS First Class & Ground Advantage Rates
Calculating postage correctly is essential for ensuring your mail arrives without delays or "postage due" notices. This calculator helps you estimate the retail postage costs for United States Postal Service (USPS) mailings, specifically focusing on letters, large envelopes (flats), and light packages.
1. First-Class Mail (Letters and Flats)
For standard envelopes and large envelopes, pricing is primarily determined by weight, provided the item meets specific dimensional standards.
Letters (1 oz – 3.5 oz): The standard retail rate usually starts at a base price for the first ounce (currently $0.73), with an additional charge for each extra ounce (currently $0.24). If a letter exceeds 3.5 ounces or is rigid/lumpy, it is classified as a Large Envelope.
Large Envelopes / Flats (1 oz – 13 oz): These are larger than letters (e.g., 9×12 or 10×13 envelopes). They must be flexible and uniformly thick. If a Flat is rigid, more than 3/4-inch thick, or varies in thickness, it must be mailed as a Package.
In July 2023, USPS consolidated First-Class Package Service into a new service called USPS Ground Advantage. For packages weighing less than 16 ounces (15.99 oz), this remains the most economical option for small items.
Unlike letters, package pricing depends on two factors:
Weight Tier: Prices are grouped into tiers (up to 4 oz, up to 8 oz, up to 12 oz, and up to 15.99 oz).
Shipping Zone: The distance the package travels affects the price. Zone 1 represents local shipments, while Zone 9 represents the furthest US territories.
3. Determining Your Zone
The "Zone" is determined by the distance between your origin Zip Code and the destination Zip Code. You cannot simply guess the zone based on state alone, as it is a radius calculation. However, generally:
Zones 1-2: Within ~150 miles.
Zone 4: ~300-600 miles.
Zone 8: Over 1800 miles (Coast to Coast).
4. Dimensional Requirements
Price isn't just about weight; shape matters. A "Letter" must be rectangular. A square envelope often requires extra postage (non-machinable surcharge). A "Flat" must be flexible. If you put a pen or a hard object inside a standard envelope, it makes it "non-machinable" or upgrades it to a "Package" rate, which is significantly more expensive than a stamp.
Note: This calculator uses standard Retail rates. If you purchase postage online through commercial platforms (like eBay, PayPal, or Pirate Ship), you may access "Commercial Pricing," which is typically cheaper than the rates shown at the Post Office counter.