Usps First Class Postage Rate Calculator

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Postage Calculator

Standard Letter (Stamped) Standard Letter (Metered) Large Envelope (Flat) Postcard
Standard rectangular envelopes.
USPS rounds up to the next ounce.
Mail Class: First-Class Mail
Weight (Billable): 0 oz
Base Rate (1st oz): $0.00
Additional Ounces: $0.00
Total Postage: $0.00

USPS First-Class Postage Rate Calculator

Calculating the correct postage for your mail is essential to ensure it reaches its destination without being returned or arriving with "postage due." This calculator helps you estimate the cost of sending Letters, Large Envelopes (Flats), and Postcards via USPS First-Class Mail Domestic based on current rates.

How First-Class Mail Rates Work

USPS postage pricing for First-Class Mail is primarily determined by the shape of the mailpiece and its weight. The pricing structure separates items into distinct categories:

  • Standard Letters: Ordinary envelopes used for bills, greeting cards, and letters. They must be rectangular and machine-processable.
  • Large Envelopes (Flats): Larger than standard letters (e.g., 9×12 envelopes) but must be flexible and uniformly thick.
  • Postcards: Single sheet rectangular cards within specific size limits.

Weight Rounding Rule

A critical rule in USPS postage calculation is weight rounding. Postage is not calculated on fractional ounces. Any fraction of an ounce is rounded up to the next whole ounce. For example, a letter weighing 1.1 ounces is charged at the 2-ounce rate.

Current Rate Structure (Reference)

Postage rates fluctuate periodically. This calculator uses the standard retail rates effective from mid-2024. Below is a breakdown of the base costs:

Mail Type Price for First Ounce Each Additional Ounce Max Weight
Standard Letter (Stamped) $0.73 $0.28 3.5 oz
Standard Letter (Metered) $0.69 $0.28 3.5 oz
Large Envelope (Flat) $1.50 $0.28 13 oz
Postcard $0.56 N/A N/A

Size and Shape Restrictions

Letters: Must be at least 3.5 inches by 5 inches. Maximum size is 6.125 inches by 11.5 inches. Thickness cannot exceed 1/4 inch. If a letter is rigid, square, or has an uneven surface (like a clasp), a "non-machinable surcharge" ($0.44) may apply (not included in this basic calculator).

Large Envelopes (Flats): Must have one dimension greater than 6.125 inches high OR 11.5 inches long OR 1/4 inch thick. Maximum size is 12 inches by 15 inches by 3/4 inch thick.

Overweight Items: Letters over 3.5 oz are charged as Large Envelopes. Large Envelopes over 13 oz are no longer eligible for First-Class Mail and must be sent via USPS Ground Advantage or Priority Mail.

function updateWeightLimit() { var type = document.getElementById('mailType').value; var note = document.getElementById('typeNote'); if (type === 'postcard') { note.innerText = "Max size: 4.25\" x 6\". Thickness: 0.007\" to 0.016\"."; } else if (type === 'flat') { note.innerText = "Max weight: 13 oz. Must be flexible."; } else { note.innerText = "Max weight: 3.5 oz. Must be rectangular."; } } function calculatePostage() { // Inputs var mailType = document.getElementById('mailType').value; var weightRaw = parseFloat(document.getElementById('weightOz').value); var errorDiv = document.getElementById('errorMsg'); var resultDiv = document.getElementById('result-container'); // Reset display errorDiv.style.display = 'none'; errorDiv.innerText = "; resultDiv.style.display = 'none'; // Validation if (isNaN(weightRaw) || weightRaw 3.5oz automatically for user convenience? // Strictly, letters > 3.5oz ARE flats. However, let's enforce limits per selection for clarity. if (mailType === 'letter_stamped') { baseRate = 0.73; maxWeight = 3.5; typeName = "Standard Letter (Stamped)"; if (weightRaw > 3.5) { errorDiv.innerText = "Standard letters cannot exceed 3.5 oz. Please select 'Large Envelope (Flat)'."; errorDiv.style.display = 'block'; return; } // Calculation: Base for 1st oz + (Total Ounces – 1) * Add'l Rate totalCost = baseRate + ((billableWeight – 1) * additionalOzRate); } else if (mailType === 'letter_metered') { baseRate = 0.69; maxWeight = 3.5; typeName = "Standard Letter (Metered)"; if (weightRaw > 3.5) { errorDiv.innerText = "Standard letters cannot exceed 3.5 oz. Please select 'Large Envelope (Flat)'."; errorDiv.style.display = 'block'; return; } totalCost = baseRate + ((billableWeight – 1) * additionalOzRate); } else if (mailType === 'flat') { baseRate = 1.50; maxWeight = 13; typeName = "Large Envelope (Flat)"; if (weightRaw > 13) { errorDiv.innerText = "Large Envelopes over 13 oz must be sent via USPS Ground Advantage or Priority Mail."; errorDiv.style.display = 'block'; return; } totalCost = baseRate + ((billableWeight – 1) * additionalOzRate); } else if (mailType === 'postcard') { baseRate = 0.56; typeName = "Postcard"; // Postcards don't really have weight steps like letters, they must meet dim criteria. // Assume 1 unit cost regardless of weight if it fits card dimensions (usually cardstock). // Validating weight for postcard is tricky, usually just max dimensions. // We will charge flat rate. totalCost = baseRate; billableWeight = "N/A"; additionalOzRate = 0; } // Formatting var extraCost = totalCost – baseRate; if (extraCost < 0) extraCost = 0; // Display Results document.getElementById('resClass').innerText = typeName; document.getElementById('resWeight').innerText = (typeof billableWeight === 'number') ? billableWeight + " oz" : billableWeight; document.getElementById('resBase').innerText = "$" + baseRate.toFixed(2); if (mailType === 'postcard') { document.getElementById('resExtra').innerText = "N/A"; } else { document.getElementById('resExtra').innerText = "$" + extraCost.toFixed(2); } document.getElementById('resTotal').innerText = "$" + totalCost.toFixed(2); resultDiv.style.display = 'block'; }

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