Glass jar pack layout

What the calculator solves

Use this tool for a first-pass packing layout and shipping-weight estimate for a rectangular jar pack. It returns a grid, unused cells, an outer envelope, actual weight and a billable whole-pound estimate. It does not choose a carrier service, quote a rate or certify protection.

Jar and cushion inputs

Enter jar diameter and height in inches, filled jar weight in ounces and a whole-number jar count. The per-jar cushion is clearance on each side of a jar, so 2 inches adds 4 inches to the cell side used on both grid axes. The outer-box cushion surrounds the entire inner pack, adding twice its value to length and width and to top and bottom height. Keep these fields separate: one spaces jars, the other spaces the inner pack from the outer box.

How the grid is chosen

The calculator tests column counts from 1 up to the ceiling of the square root of the jar count. For each count it derives rows, multiplies rows and columns by cell size for the inner dimensions, and scores footprint area. The smallest area wins. Equal-area layouts favor the one whose inner length and width are closer together; if balance is also equal, the earlier column count remains because replacement is strict. The displayed grid is a rows-by-columns layout, and unused cells are rows times columns minus jar count.

Outer envelope and dimensional weight

Inner length and width come from the chosen rows and columns. The outer envelope adds twice the outer-box cushion to each. Height is jar height plus twice the per-jar cushion plus twice the outer-box cushion. Envelope dimensions are rounded to at most two decimals for display, so whole values such as 14 appear without trailing zeros. For dimensional weight, each outer dimension is rounded up to the next whole inch, multiplied, and divided by your parcel DIM divisor. The divisor is user-entered, so the result reflects your divisor, not a carrier rule.

Actual weight and billable estimate

Actual weight is jar count times filled jar weight in ounces, divided by 16, plus all packaging weight in pounds. Include outer box, inner box, dividers and cushioning you want counted. Displayed actual weight is rounded to two decimals. The billable whole-pound estimate takes the larger of computed actual weight and dimensional weight, then rounds up to the next whole pound. Rounding uses computed values before display rounding, so a displayed value just under a pound can still produce the next pound. This is an estimate, not a carrier invoice.

Worked starting case

With a 2.8 inch diameter, 4 inch height, 6 jars, 9 ounces per filled jar, 2 inches per-jar cushion, 3 inches outer-box cushion, 2 pounds packaging and divisor 139, the grid is 3 by 2 with no unused cells. Inner footprint is 20.4 by 13.6 inches; outer envelope is 26.4 by 19.6 by 14 inches.

Actual weight is 6 times 9 ounces divided by 16 plus 2 pounds, or 5.38 pounds displayed. Dimensional weight uses 27 by 20 by 14 inches divided by 139, about 54.39 pounds. The larger value is dimensional weight, so the billable whole-pound estimate is 55 pounds. The gap between actual and dimensional weight is the operational signal: cushion and outer clearance can dominate.

Worked changed case

Change only jar count from 6 to 7. The grid becomes 7 by 1 with no unused cells. Inner footprint is 47.6 by 6.8 inches; outer envelope is 53.6 by 12.8 by 14 inches. Actual weight rises to 5.94 pounds displayed because one more 9 ounce jar is included.

Dimensional weight uses 54 by 13 by 14 inches divided by 139, about 70.71 pounds. The billable whole-pound estimate becomes 71 pounds. The extra jar changes the selected grid shape, not just weight, so the dimensional estimate jumps sharply. Test whether a different cushion or arrangement is worth trying before treating this as final.

Limits and practical checks

Cushion values are design inputs, not a validated protection rating. The model omits board thickness, dividers, tolerances and real-world compression. It does not prove transit survival or carrier acceptance. Test a representative filled pack before committing. Use the output to compare scenarios, then confirm dimensions and protection with physical samples and applicable carrier guidance.

Questions about glass jar pack layout