Tech Pack Analysis & Building a Production BOM
Lesson Contents Overview
Learning Objectives
Comprehensive Technical GuidanceTextbook & Training SOP
Tech Pack Analysis & Building a Production BOM
1. Introduction: The Technical Backbone of Apparel Manufacturing
In the ready-made garment (RMG) export industry, the Technical Design Package (Tech Pack) is the definitive contract between the buyer's design team and the manufacturing factory. It serves as the architectural blueprint of the garment. Every detail—from seam construction and fabric weight to button placement and carton packaging—is governed by this document.
For a professional merchandiser, the ability to dissect a Tech Pack with mathematical precision and translate it into an actionable Production Bill of Materials (BOM) is the single most critical technical skill. A minor oversight—such as missing an interlining callout or misreading fabric cuttable width—can erase hundreds of thousands of dollars in factory profitability or cause catastrophic delivery cancellations.
2. Comprehensive Anatomy of a Buyer Tech Pack
A standard buyer Tech Pack spans anywhere from 5 to 25 pages depending on the complexity of the style. Merchandisers must systematically audit each of the seven core sections:
BUYER TECH PACK STRUCTURE
A. Style Header & Order Summary
- Style Number & Name: The primary alphanumeric tracking reference (e.g., Style # PL-9402 Men's Engineered Stripe Polo).
- Buyer, Division & Season: Defines commercial terms, branding guidelines, and testing protocols (e.g., Spring/Summer 2027 Men's Casual).
- Target Delivery Date & Order Quantity: Establishes the lead-time timeline for the Time & Action (T&A) calendar.
B. Technical Design CAD Sketches
- Front, Back, and Side Projections: Accurate flat sketches illustrating design lines, pockets, yokes, darts, pleats, vents, and cuffs.
- Internal Construction Details: Cross-sectional diagrams displaying waistband fusing, pocket bag construction, placket box-x stitching, and collar stands.
- Stitch Callouts: Specific stitch designations (e.g., 1/4" double needle topstitch, 4-thread overlock with 1/8" gauge).
C. Fabric Technical Specifications
- Fiber Composition: Exact percentage breakdown (e.g., 95% Combed Cotton, 5% Elastane).
- Fabric Structure & Yarn Count: Knitted (Single Jersey, Pique, Interlock, French Terry) or Woven (Twill, Poplin, Denim, Canvas) with yarn counts (e.g., 30s/1 Combed Ring Spun).
- Weight & Finish: Fabric weight in grams per square meter (e.g., 220 GSM ± 5%) and finishing requirements (Peach finish, Enzyme wash, Silicone soft, Anti-pilling, Water-repellent).
- Usable Cuttable Width: The true width usable by CAD markers (e.g., 58" Cuttable on 60" Total Width).
3. Garment Construction & Stitch Classifications
Garment durability, appearance, and sewing thread consumption depend entirely on the ISO 4915 / ASTM D6193 stitch types specified in the Tech Pack.
Stitch Class Breakdown
- Class 301 (Lockstitch): Formed with two threads (needle and bobbin). It does not stretch and is reversible. Used for topstitching, collar setting, pocket attaching, and general woven garment assembly.
- Class 401 (Two-Thread Chainstitch): Formed with one needle thread and one looper thread. It provides excellent longitudinal elasticity and high seam strength. Essential for denim outseams, trouser inseams, and knitted waistband attachments.
- Class 504 / 514 (Overlock / Mock Safety): Trims fabric edges while binding them. 3-thread overlock is standard for knit T-shirt side seams; 4-thread mock safety is required for high-stress activewear seams.
- Class 602 / 605 (Coverstitch / Flatlock): Features top cover and bottom looper threads. Widely used for bottom hemming, sleeve cuffs, and decorative flat seam joins in sportswear.
4. Measurement Specification Sheet & Tolerances
The Measurement Spec Sheet provides the physical dimensions for garment construction across the entire size range.
SAMPLE SPEC SHEET (MEN'S POLO SHIRT) - SIZES IN CM
| POINT OF MEASURE | CODE | S | M | L | XL | XXL | TOLERANCE (+/-) |
|---|---|---|---|---|---|---|---|
| 1. Body Length HPS 2. 1/2 Chest Width 3. Across Shoulder 4. Sleeve Length 5. Collar Length 6. Placket Width 7. Placket Length | A01 B01 C01 D01 E01 F01 F02 | 70.0 50.0 42.0 21.0 40.0 3.2 15.0 | 72.0 53.0 44.0 22.0 41.5 3.2 15.0 | 74.0 56.0 46.0 23.0 43.0 3.2 15.0 | 76.0 59.0 48.0 24.0 44.5 3.2 15.0 | 78.0 62.0 50.0 25.0 46.0 3.2 15.0 | 1.0 cm 0.8 cm 0.5 cm 0.5 cm 0.5 cm 0.2 cm 0.3 cm |
Key Rule on Tolerances: Manufacturing tolerance is the permissible limit of variation. If a medium polo length is 72.0 cm with a ±1.0 cm tolerance, any garment measuring between 71.0 cm and 73.0 cm passes inspection. A garment measuring 70.8 cm is rejected as a defect.
5. Step-by-Step Tech Pack Auditing SOP
Merchandisers should follow this 6-step audit SOP immediately upon receiving a Tech Pack:
- Step 1: Check Version Control & Change Log: Verify revision number and cross-reference buyer modification notes against the previous version.
- Step 2: Reconcile Sketch against Spec Table: Ensure all visible design elements (e.g., chest pocket, side slit tape) have corresponding entries in the measurement table and trim list.
- Step 3: Audit Fabric Feasibility: Confirm yarn count, structure, and GSM combination are knit-feasible without spirality, bowing, or excessive shrinkage.
- Step 4: Audit Trim Nominations: Verify whether buyer-nominated suppliers have operational liaison offices, local stocks, or long import lead times.
- Step 5: Review Artwork Scalability: Check if chest prints scale proportionately across small and plus sizes, or if static artwork screens are used.
- Step 6: Raise Formal RFI Log: Consolidate all technical ambiguities into an official Request for Information email table.
Professional Buyer RFI Email Template
6. What is a Production BOM & How to Build It
A Production Bill of Materials (BOM) is an itemized register detailing every raw material, trim, embellishment, and packaging item required to manufacture one unit (or one dozen units) of a garment.
The Core BOM Equations
Gross Consumption = Net Consumption × ≤ft(1 + Wastage %100)
Extended Item Cost = Gross Consumption × Unit Price
Total Material Cost / Dzn = (Extended Item Costs)
Categories in a Production BOM
- Fabric Components: Shell fabric, contrast panels, rib collar/cuffs, pocketing bags, and fusible interlinings.
- Sewing & Assembly Trims: Sewing threads (spun poly, core-spun, texturized poly), main brand labels, care/size labels, buttons, rivets, zippers, elastics, drawcords, eyelets, and seam sealing tapes.
- Packaging Materials: Individual polybags, blister packs, silica gel desiccant bags, hangtags, price tickets, joker tags, size stickers, tissue paper, master corrugated cartons, carton gum tape, and polypropylene strapping bands.
7. Sample BOM vs. Bulk Production BOM
| SAMPLE BOM | BULK PRODUCTION BOM |
|---|---|
| • Uses estimated yardage / weight • Retail or local trim pricing • Higher wastage buffer (15 - 25%) • Substitute colors/hangtags • Used for proto sample costing | • Uses finalized CAD marker yield • Negotiated mill contract rates • Lean, audited wastage (3 - 8%) • 100% buyer-nominated approvals • Directly triggers ERP PO release |
8. Common BOM Traps & Merchandiser Checklist
1. Standard Buyer Tech Pack Component Anatomy
| Tech Pack Section | Key Information Contained | Merchandiser Action Required | Responsible Factory Department |
|---|---|---|---|
| 1. Style Header & Summary | Style #, Season, Brand/Division, Target FOB, Garment Category, Order Qty | Verify style reference consistency across PO and tech pack versions | Merchandising (Lead) |
| 2. Technical CAD Sketch | Front, Back, Side, Inside views with construction callouts and seam details | Analyze stitch types, seam allowances, plackets, collar construction | Pattern Room & Sampling |
| 3. Fabric Specifications | Composition, Construction, Yarn Count, Finished GSM, Cuttable Width, Finish | Source lab dips, yarn bookings, calculate initial fabric yield and shrinkage | Fabric Sourcing & Textile Lab |
| 4. Trims & Accessories (BOM) | Thread type/count, buttons (ligne), zippers, elastics, tapes, labels | Match buyer nominated suppliers, check MOQs and lead times | Trim Merchandising & Sourcing |
| 5. Artwork & Embellishment | Screen print, embroidery, heat transfer, placement, dimensions, Pantone codes | Send artwork to strike-off vendors, verify strike-off approval timeline | Embellishment & Print Dept |
| 6. Measurement Spec Sheet | Points of Measure (POM), Base Size (e.g., Size M), Grade Rules, Tolerances | Transfer specs to CAD pattern makers for grading and initial marker creation | CAD & Pattern Making |
| 7. Packing & Presentation | Folding method, hangtag placement, polybag type, carton dimension/assortment | Calculate packaging BOM, verify carton CBM and gross weight limits | Finishing & Packaging Dept |
2. Garment Sewing Stitches & ISO/ASTM Classification Reference
| Stitch Class (ISO 4915) | Standard Industry Name | Common Garment Application | Thread Consumption Ratio |
|---|---|---|---|
| Class 100 | Single Thread Chainstitch | Temporary basting, button sewing, blind hems | 1.5 to 2.0x seam length |
| Class 301 | Single Needle Lockstitch (Plain) | Woven seams, collar attaching, placket topstitch, pocket setting | 2.5 to 3.0x seam length |
| Class 401 | Two-Thread Chainstitch | Trousers inseam/outseam, denim jeans, waistband attaching | 4.5 to 5.5x seam length |
| Class 504 | 3-Thread Overlock | Knit T-shirt side seams, shoulder joining, edge trimming | 12.0 to 14.0x seam length |
| Class 514 | 4-Thread Mock Safety Overlock | Activewear seams, knit polo side seams, high-stress knit joints | 16.0 to 18.0x seam length |
| Class 516 | 5-Thread Safety Stitch | Woven shirt side seams, woven pant assembly (overlock + chain) | 18.0 to 20.0x seam length |
| Class 602 / 605 | Bottom Coverstitch / Top & Bottom Flatlock | T-shirt bottom hem, sleeve hem, neck rib topstitch, activewear | 20.0 to 30.0x seam length |
3. Complete Master Production BOM for Men's Classic Pique Polo Shirt (Style # PL-9402)
| Item Category | Material Description & Technical Spec | Supplier / Source | UOM | Unit Consumption | Wastage % | Gross Consumption | Unit Price (USD) | Cost / Dzn (USD) |
|---|---|---|---|---|---|---|---|---|
| Main Fabric | 100% Combed Cotton Pique 220 GSM, 30s/1 + 40D, 60" Cuttable, Silicone Wash | Nominated Mill (Envoy Textiles) | Kg | 2.850 kg/dzn | 8% | 3.078 kg/dzn | $6.20 / kg | $19.08 |
| Collar & Cuff | 1x1 Flat Knit Collar (42cm x 8cm) + Cuff (32cm x 3cm) Yarn Dyed Jacquard | In-House Collar Section | Sets | 12 sets/dzn | 4% | 12.48 sets/dzn | $0.65 / set | $8.11 |
| Placket Fusing | Non-Woven Microdot Interlining 45 GSM, White, 3cm x 16cm | Prym / Local Nominated | Yards | 0.45 yds/dzn | 5% | 0.473 yds/dzn | $0.35 / yd | $0.17 |
| Neck Tape | 100% Cotton Herringbone Tape 1cm Width, Dyed to Match (DTM) | Dekko / Sourcing | Meters | 4.20 m/dzn | 5% | 4.41 m/dzn | $0.08 / m | $0.35 |
| Sewing Thread | 100% Spun Polyester 40/2 DTM (Body Sewing) & 50/2 (Topstitch) | Astra Coats / Vardhman | Cones | 0.048 cones/dzn | 10% | 0.053 cones/dzn | $1.80 / cone | $0.10 |
| Buttons | 18L (11.5mm) 4-Hole Engraved Pearl Polyester Button, 3 Pcs/Garment | YKK / Local Certified | Gross | 0.250 grs/dzn | 5% | 0.263 grs/dzn | $0.85 / gross | $0.22 |
| Main Label | High-Definition Damask Woven Label (50mm x 25mm), End Fold | R-PAC / Avery Dennison | Pcs | 12 pcs/dzn | 3% | 12.36 pcs/dzn | $0.045 / pc | $0.56 |
| Care/Size Label | Printed Satin Wash Care Label with QR code + Country of Origin | Avery Dennison | Pcs | 12 pcs/dzn | 3% | 12.36 pcs/dzn | $0.025 / pc | $0.31 |
| Hangtag & String | 400 GSM Art Card Matte Laminated with Waxed Cotton Cord & Safety Pin | Buyer Nominated | Sets | 12 sets/dzn | 2% | 12.24 sets/dzn | $0.120 / set | $1.47 |
| Polybag | Self-Adhesive Recycled LDPE Polybag with Warning Text (12" x 16" x 0.04mm) | Local Green Certified | Pcs | 12 pcs/dzn | 2% | 12.24 pcs/dzn | $0.035 / pc | $0.43 |
| Master Carton | 5-Ply Corrugated Brown Box (60cm x 40cm x 30cm, Burst Test 180 lbs) | Local Certified Box Maker | Pcs | 0.250 ctn/dzn | 1% | 0.253 ctn/dzn | $1.40 / ctn | $0.35 |
| Carton Gum Tape | BOPP Transparent Adhesive Packaging Tape 2" Width | Factory Store Inventory | Rolls | 0.015 roll/dzn | 5% | 0.016 roll/dzn | $1.10 / roll | $0.02 |
Practical Commercial Flow
Junior Merchandiser Tanvir at Apex Apparels received a 14-page Tech Pack for a Women's Activewear Hoodie from a major UK brand. Upon technical breakdown, he identified three critical ambiguities: (1) The sketch showed contrast flatlock stitching on raglan seams, but the BOM listed standard lockstitch thread; (2) The fabric cuttable width was stated as 62" tubular, while the knit mill produced only 58" open-width; (3) The care label artwork omitted the EU REACH compliance symbol required for Euro shipments. Tanvir prepared a structured RFI log, secured buyer written approval for open-width marker adjustment, updated thread consumption for 4-thread flatlock (saving $0.18/dzn in thread deficit), and revised the BOM before costing sign-off.
Factory Real-Life Scenario
Scenario: A factory in Gazipur booked 60,000 yards of 100% cotton poplin based on a development Tech Pack that stated 58" cuttable width. When bulk fabric arrived, the usable cuttable width between needle holes was only 54", resulting in an automatic 7.2% pattern interlocking loss during marker making and creating a 4,300-yard fabric deficit.
Solution: The Senior Merchandiser immediately re-nested CAD markers using combo-size splitting (pairing Size S with XL and M with L), reclaimed cuttable edges with rotary cutter tolerance adjustments, and negotiated a split top-up order with the local dye house on 7-day fast-track delivery.
Impact: Saved the order from a 2-week shipment penalty and established a mandatory factory rule: Never book bulk yardage until the fabric mill delivers certified finish-width lab inspection swatches.
Commercial Officer Best Practice
Always verify the difference between Total Fabric Width and Usable Cuttable Width (pin-to-pin or needle-to-needle). Booking fabric consumption on total width instead of cuttable width is the single most common cause of fabric shortages in garment manufacturing.
Top Beginner Mistakes to Avoid
- Accepting tech pack updates verbally or over chat without requesting a formal revised Tech Pack Version number (e.g., Rev 02).
- Failing to specify the Button Ligne (L) and hole count on the trim BOM, leading to store delivery of wrong-sized buttons.
- Calculating sewing thread consumption using simple stitch length without multiplying by the specific ISO stitch thread ratio.
- Ignoring interlining shrinkage during collar and placket fusing, leading to puckering after garment wash.
- Mixing up unit conversions (e.g., entering button consumption in dozens instead of gross, creating a 12x error in booking).
Important Commercial & Trade Terminology (8 Terms)
An architectural design blueprint created by a fashion designer or buyer specifying construction, fabrics, trims, measurements, tolerances, and packaging for a garment.
💡 Note: Always check the Version Number and Date to avoid working on outdated specs.An itemized schedule of all physical raw materials, trims, embellishments, and packaging items needed to manufacture a specific style, including exact consumptions, wastage, and costs.
💡 Note: Directly uploaded into ERP to generate Purchase Orders (PO) for suppliers.The usable width of the fabric from inner selvedge to selvedge (excluding pinholes/glue edges) across which pattern pieces can be laid without defects.
💡 Note: Never calculate markers using overall fabric roll width.The standard worldwide unit of measure for button diameter, where 1 Ligne = 0.635 mm (or 1/40th of an inch). Example: 18L = 11.43 mm (shirt front), 24L = 15.24 mm (jacket front).
💡 Note: Always mention both Ligne and line thickness in the trim BOM.A commercial unit of count equal to 12 Dozens or 144 Pieces. A Great Gross equals 12 Gross (1,728 Pieces).
💡 Note: Standard trading unit for buttons, rivets, and snap fasteners.The number of individual stitches formed within one linear inch of seam. Higher SPI gives higher seam strength but requires more thread and sewing time.
💡 Note: Knitwear standard is 10–12 SPI; high-end dress shirts require 16–18 SPI.Standardized physical locations on a garment (e.g., Across Shoulder, 1/2 Chest, HPS Body Length) where QA measures against the spec sheet.
💡 Note: Always cross-check POM definitions with buyer spec manual.A formal technical query logged by the factory merchandiser asking the buyer to clarify missing or conflicting tech pack details.
💡 Note: Never proceed with assumptions without written buyer RFI approval.Interview Preparation Questions & Answers (5 Questions)
Master these high-frequency interview questions for Commercial Officer, Merchandising, and Export Executive roles.
A Tech Pack is the technical blueprint of a garment. Upon receipt, a merchandiser must first inspect: (1) Style Summary & Order Quantity, (2) Fabric Specs (composition, GSM, cuttable width), (3) Construction details & stitch classes, (4) Trim/Accessory nominations, (5) Measurement Spec Sheet with grade rules and tolerances, and (6) Packing instructions. Early inspection flags lead-time bottlenecks and costing risks.
Frequently Asked Questions (4 FAQs)
Clear, beginner-friendly answers to the most common questions about the Commercial Department.
Key Takeaways & Summary Points
Executive Lesson Summary
The Tech Pack is the fundamental operational and legal blueprint provided by the buyer. By conducting a systematic audit of sketches, construction seams, fabric parameters, trim cards, artwork, measurements, and packaging instructions, merchandisers eliminate costly ambiguities. Converting the Tech Pack into an audited Production BOM ensures accurate material bookings, tight cost controls, and smooth cross-functional factory execution.
Lesson Downloads & SOP Templates
Fabric Consumption Calculator
Calculate fabric consumption per garment for costing and booking.
Open ToolGarment Merchandising Process: From Order Confirmation to Shipment
Comprehensive industry standard guide.
Read Guide