Knitted Bag ROI: Seven Steps in Order, With a Calculation Any Buyer Can Recompute

The Decision Order: Seven Steps Before Any Number

A knitted bag ROI calculation is run in seven steps in a fixed order, because each step supplies an input the next one needs: baseline, cost classification, service life, freight and duty delta, return cost, calendar value, then sensitivity.

The order is not cosmetic. Service life cannot be valued until recurring cost is separated from one-off cost, because the two amortise differently; the freight delta cannot be computed until the packing method is fixed, because a cube change moves it; and the sensitivity cannot be run until every other step has produced a variable rather than an assertion. Buyers who skip to the unit-price comparison end up with a number that is arithmetically correct and commercially meaningless, which is the usual reason a knitted programme is approved for the wrong reason and reversed after one season.

• Step one: fix the comparison baseline, so both routes are measured against the same bag.
• Step two: classify every cost as one-off or recurring, because the two amortise differently.
• Step three: put a number on service life, which converts a unit cost into a cost per use.
• Step four: compute the freight and duty delta, which is where a knit wins or loses on cube.
• Step five: subtract return and defect cost, using the inspection level rather than hope.
• Step six: value the calendar, because a shorter cycle is working capital released.
• Step seven: run a sensitivity across three volumes rather than trusting one point estimate.

Step One: Fix the Comparison Baseline

The baseline is one bag specified identically on both routes — same dimensions, same hardware, same test thresholds — and without it every later step produces a number that cannot be defended.

In practice the baseline is a short written specification: a 380 by 380 mm tote with a base, 320 g/m², gauge E12, one size 5 coil zip, one pair of ring tabs, about 20,000 Martindale rubs to ISO 12947-2 and roughly 600 N of strip tensile strength to ISO 13934-1. With that written down, a knitted quotation and a sewn quotation are comparable, and the difference between them is a route difference rather than a specification difference. Without it, the two quotes describe two different bags and the ROI is a comparison of nothing.

Baseline dimensions

380 by 380 mm tote with a base and handles, one silhouette across the range

Fabric specification

320 g/m² at gauge E12 in 300D polyester

Hardware

One size 5 coil zip and one pair of ring tabs, so the component count is held constant

Abrasion threshold

About 20,000 Martindale rubs to ISO 12947-2

Tensile threshold

Roughly 600 N of strip tensile strength to ISO 13934-1

Reference unit

USD 4.80 FOB Xiamen on the knitted route

Minimum per colourway

100 pcs per style and colourway

Step Two: Separate One-Off From Recurring Cost

One-off costs amortise across the life of the programme and recurring costs do not, so mixing them is the error that makes a small programme look worse than it is and a large one look better.

On the knitted route the one-off block is three items: programming at USD 180 per stitch file, sampling at USD 45 per piece credited against bulk, and compliance screening at about USD 350 per material. The recurring block is the unit itself, freight and duty. The useful property of the one-off block is that it is recoverable: the file runs again next season at no charge, and the screen stays valid while the material and destination market are unchanged. A buyer planning more than one season should therefore amortise the one-off block across the total of both seasons rather than across the first drop, and doing so typically halves its loading per unit.

Step Three: Put a Number on Service Life

Service life converts a unit cost into a cost per use, and it is the step that most often reverses the conclusion of the unit-price comparison.

The calculation is landed cost divided by expected uses. Suppose the knitted route lands at about USD 7.15 per piece and a bag in daily use is carried roughly 220 times a year over a service life of 24 months, which is about 440 uses: the cost per use is about USD 0.016. Now suppose an alternative route lands lower per piece but lasts 18 months, which is about 330 uses at the same rate: if it lands at USD 6.20, its cost per use is about USD 0.019. The route with the higher landed figure wins on the measure a brand actually cares about, and it wins by a margin that no unit-price negotiation would have revealed.

Step Four: Add the Freight and Duty Delta

Freight and duty are the largest single delta between two routes that look close on unit price, and on a knitted bag freight is decided by cube rather than by weight.

A knitted body recovers from compression, so flat packing is viable and the carton cube falls against a structured sewn equivalent. Sea freight at about 21 days costs roughly USD 0.31 per piece on this product class, and a quarter reduction in cube moves that line by roughly the same proportion. Duty is a rate applied to customs value and follows the HS classification in the destination market, so it is a planning allowance of about 12% until the importer confirms it. Both belong in the ROI as deltas rather than as absolutes, because the question is not what freight costs but how much more or less it costs on one route than the other.

Step Five: Subtract Return and Defect Cost

Return and defect cost is subtracted rather than added, because it is the part of the shipped volume that produces no value, and it is the line most often omitted from an ROI entirely.

The defect side is bounded by inspection: release runs against AQL 2.5 to ISO 2859-1, which sets the sample size and the accept and reject numbers, so the exposure is a known distribution. The commercial side is a rate and has to be estimated: a return allowance of about 2.4% of units shipped is a reasonable planning figure for a bag in general retail. Applied to the worked example, 2.4% of 600 pieces is about 14 units that produce no value, so the effective volume in the cost-per-use calculation is 586 rather than 600. A buyer who omits that adjustment will overstate the return by roughly the same percentage, which is small in isolation and material across a range.

Step Six: Value the Calendar, Not Just the Unit

A shorter cycle is working capital released, and on a knit programme the calendar is 7 working days of sampling plus 30 days of bulk, which is short enough to be worth pricing.

The mechanism is stock cover. A cycle of about 58 calendar days including transit requires roughly 8 to 9 weeks of cover at the reorder trigger; a longer alternative cycle requires more, and the difference is cash sitting in a warehouse rather than on a shelf. On a programme of 600 pieces at a landed figure of about USD 7.15, three additional weeks of cover is about USD 1,600 of working capital held for the length of the season. That is not a cost in the accounting sense and it does not appear on the quotation, which is precisely why it is excluded from most ROI calculations and why including it changes decisions that looked settled.

Step Seven: Run the Sensitivity, Not the Point Estimate

A single ROI figure is an assertion; three figures across a volume range are a decision, because they show where the conclusion changes and therefore which variable to verify first.

At 100 pieces the one-off block loads about USD 6.20 per unit and dominates, so the ROI is most sensitive to whether the programme repeats and can reuse the file. At 600 pieces the freight and duty block dominates, so it is most sensitive to packing method and mode. At 1,200 pieces the unit dominates, so it is most sensitive to GSM and component count. Running all three takes minutes and produces something a point estimate cannot: the identity of the variable that would change the answer, which is the only thing worth spending verification time on.

A Worked ROI Calculation With Named Variables

The worked calculation below uses named variables only, so any buyer can substitute their own figures and reach their own answer.

1. Quantity Q = 600 pcs across two colourways, so 300 per colourway against the 100 pcs minimum.
2. Unit U = USD 4.80 FOB Xiamen at 320 g/m² and gauge E12, so the unit block is USD 2,880.
3. Programming P = USD 180, one file shared across both colourways, amortised to USD 0.30 per piece now and USD 0.15 across two seasons.
4. Sampling S = USD 45 times 3 = USD 135, credited against bulk, so a net of zero at confirmation.
5. Screening C = USD 350 times 2 materials = USD 700, or USD 1.17 per piece now and about USD 0.58 across two seasons.
6. Freight F = USD 0.31 times 600 = USD 186 by sea at about 21 days.
7. Duty D = about 12% of the USD 2,880 customs value, so roughly USD 346.
8. Landed L = 2,880 plus 180 plus 700 plus 186 plus 346 = about USD 4,292, or about USD 7.15 per piece.
9. Return adjustment R = 2.4% of 600, so about 14 units and an effective volume of 586.
10. Service life = 24 months at about 220 carries a year, so about 440 uses and about USD 0.016 per use.

Two readings follow. Across two seasons at the same volume, the programming and screening lines are reused, so the landed figure falls from about USD 7.15 to roughly USD 6.88 per piece without any change to the specification. And the sensitivity is concentrated: if freight mode changes from sea to air, the landed figure rises by roughly USD 1.24 per piece, which is larger than every other lever in the model combined. That is the variable to verify first, and it is a calendar decision rather than a purchasing one.

When the Answer Is No

The honest output of this calculation is sometimes negative, and three conditions produce that result consistently: a frozen shape at high volume, a market with a high duty rate on the knitted classification, and a single-season programme with no reuse.

Above roughly 1,200 pieces with a shape that will not change, a cut-and-sew floor tuned for repetition can produce the same bag for less per unit, and the knitted advantages on waste and cube may not close the gap. Where the destination market classifies a knitted bag at a materially higher duty rate than a sewn equivalent, the duty delta can exceed the freight saving entirely, so classification should be confirmed before the calculation is trusted. And where there is genuinely only one season, the one-off block amortises across a single drop and its loading per unit is at its highest. None of those three make the knitted route wrong; they make it wrong for that programme, which is a different and more useful conclusion.

Frequently Asked Questions

People Also Ask

The Order Produces the Answer

A knitted bag ROI is not a number to be found but an order to be followed. Fix the baseline, classify the costs, value the life, add the delta, subtract the returns, price the calendar, and only then run the sensitivity — because each step supplies an input the next one cannot invent.

For the fixed-cost structure behind step two, see bag programme cost planning. For the objections that follow a positive result, see knitted bag buyer objections, answered, and for the decision the calculation supports, see why brands switch to knitted bags.