FBA Box Size and Weight Limits, Explained

Why you must verify FBA limits yourself

Fulfillment-by-Amazon carton rules can cover box weight, dimensions, the number of units per box, labeling, and how cartons are palletized. These requirements are set in your seller agreement and the current FBA help pages, and they may change over time. Because we cannot verify the current numbers from an authoritative source in this guide, we will not state specific FBA limits as fact.

Log into Seller Central and check the current requirements for your marketplace, products, and shipment. Record all applicable carton dimensions, weight limits, unit-count restrictions, labeling rules, and any exceptions or special handling instructions. Separately check your carrier's current service and contract rules; the carrier guidance below does not replace Amazon's requirements.

• Confirm current FBA box weight and dimension limits in Seller Central before every new product launch.
• Check whether your items fall under standard-size or oversize handling, since prep rules differ.
• Keep a dated note of the limits you verified, so your team can spot when requirements shift.

How to measure a box the way carriers do

UPS instructs shippers to measure the longest side first and call it length, then rotate the package to measure the next longest side as width, and the remaining side as height. UPS rounds each measurement up to the next whole inch before any math is done, so a 20.25 inch side counts as 21 inches. FedEx publishes the same length plus girth formula, but confirm its measuring and rounding conventions in your own FedEx agreement.

Length plus girth is the measurement that trips people up. Girth is the distance around the box, calculated as twice the width plus twice the height. So length plus girth equals length plus two times width plus two times height. A box that is 30 inches long, 20 inches wide, and 15 inches high has a length plus girth of 30 plus 40 plus 30, which is 100 inches.

• Measure the longest side first and call it length.
• For the cited UPS measurement method, round each dimension up to a whole inch. Verify Amazon's and other carriers' measurement conventions separately.
• Length plus girth equals length plus two times width plus two times height.

Dimensional weight, the cost driver behind box size limits

Dimensional weight reflects package volume relative to actual weight. The cited UPS page lists divisors of 139 for Daily Rates and 166 for Retail Rates. The cited FedEx guide uses 139 for U.S., Puerto Rico, and international shipments and compares dimensional weight with actual weight to determine chargeable weight. Confirm the applicable service, divisor, dimension and weight rounding, and billing provisions for your shipment rather than treating these published examples as universal rules.

This is why oversized cartons can cost more to ship than their contents suggest. A big lightweight box of pillows can be billed as if it were far heavier than it is. Right-sizing your master carton is worth evaluating whenever dimensional weight exceeds actual weight.

• Multiply length by width by height in inches to get cubic size, using the applicable carrier's dimension-rounding rules.
• Divide cubic size by the applicable divisor to get dimensional weight in pounds. The cited UPS method rounds any fractional result up to the next whole pound; verify the rule for your service.
• The cited FedEx guide uses the greater of actual and dimensional weight. Confirm applicable weight rounding and other billing provisions for your shipment.

A worked example: comparing two master cartons

Suppose a hypothetical seller ships a small, lightweight product to FBA. The seller is choosing between two master cartons that both hold the same hypothetical unit count with adequate cushioning. Carton A is 24 by 18 by 16 inches and weighs 22 pounds packed. Carton B is 20 by 14 by 12 inches and weighs 19 pounds packed. All dimensions are already whole numbers, so no rounding is needed. The example uses the UPS daily rate divisor of 139 and the UPS rule of rounding up to the next whole pound.

Carton A: multiply 24 by 18 by 16 to get 6,912 cubic inches. Divide 6,912 by 139 to get about 49.7 pounds, which rounds up to 50 pounds of dimensional weight. Since 50 exceeds the 22 pound actual weight, the chargeable weight is 50 pounds.

Carton B: multiply 20 by 14 by 12 to get 3,360 cubic inches. Divide 3,360 by 139 to get about 24.2 pounds, which rounds up to 25 pounds. Actual weight is 19 pounds, so chargeable weight is 25 pounds. In this hypothetical, Carton B cuts chargeable weight in half. Before switching, confirm that the smaller carton physically fits your real unit count plus cushioning. These numbers are an illustrative arithmetic exercise, not a quote or market benchmark, and your carrier contract's divisor may differ.

• Carton A: 24 x 18 x 16 = 6,912 cubic inches; 6,912 divided by 139 is about 49.7, rounded to 50 pounds dimensional weight.
• Carton B: 20 x 14 x 12 = 3,360 cubic inches; 3,360 divided by 139 is about 24.2, rounded to 25 pounds dimensional weight.
• Chargeable weight is the greater of actual and dimensional weight for each carton.

Box strength: matching board grade to packed weight

• Read the Box Maker's Certificate on your actual boxes and never pack beyond the stated gross weight.
• UPS describes these size ranges as manufacturable box sizes based on board strength, not carrier length-plus-girth limits. The supplied excerpt does not define how to calculate this size metric, so do not use this column to approve carton dimensions. Bursting strength and edge-crush strength measure different properties; the paired values are not conversions or proof of equivalent performance. Use the actual box specification and appropriate packed-product evaluation.

Packing recommendations for fulfillment shipments

General carrier packing guidance can inform planning but does not establish FBA acceptance or adequate protection for every product. UPS recommends at least two inches of appropriate cushioning between items and container surfaces. FedEx recommends double-boxing fragile items, using an outer box at least 6 inches longer, wider, and deeper than the inner box, with at least 3 inches of cushioning around it and H-pattern taping. Check the outer box's usable internal dimensions against the inner box's exterior dimensions so the specified cushioning actually fits on every side.

UPS advises avoiding reused boxes, and FedEx asks for sturdy, undamaged boxes with all flaps intact. For an FBA master carton, we recommend a sturdy new corrugated box, cushioning that restricts product movement, and clean surfaces for current labels, placed according to current FBA prep rules.

• Use the cited UPS recommendation of at least 2 inches of appropriate cushioning as a planning reference, then evaluate protection for your product and applicable FBA prep rules.
• For fragile items, consider the cited double-box method and verify usable clearance for at least 3 inches of cushioning on every side of the inner box.
• Seal with H-pattern taping on the center seam and both edges.
• As a practical recommendation, avoid damaged boxes and remove or cover any old labels.

Decision table: what to check before shipping to FBA

Pre-shipment checklist

This checklist is Teal Packaging's editorial planning framework. The cited sources support only the specific carrier principles noted, and FBA-specific limits must come from your own Seller Central verification.

• Record the FBA box weight, dimension, and units-per-box limits you verified today, with the date.
• Measure each packed carton's exterior dimensions, longest side first. Apply Amazon's measurement rules for FBA checks and the applicable carrier's rounding rules for shipping calculations.
• Calculate length plus girth: length plus two times width plus two times height.
• Calculate dimensional weight using the applicable divisor and service-specific dimension and weight rounding.
• Compare actual versus dimensional weight and note the chargeable figure.
• Check the Box Maker's Certificate against packed weight.
• Confirm cushioning, taping, and label placement per current FBA prep rules.
• Photograph one packed carton for your records in case of a receiving dispute.

Scope and limits

This guide covers general box measurement, dimensional weight arithmetic, and carrier packing principles. It does not determine FBA compliance, does not state current Amazon limits, and does not cover hazardous materials, temperature-controlled goods, or palletized LTL freight, each of which has separate requirements you must verify with Amazon and your carrier. Arithmetic here is an estimate, not a substitute for a scale, a tape measure, and any testing your products require.

Questions about FBA box size and weight limits