Tube Neckline Sweatshirt

What This Design Is

A loose, knit garment with a wide dropped shoulder fit, a flattened sleeve cap, banded hem and cuffs, and a soft rounded tube neckline instead of a ribbed neckband. Comfortable enough for loungewear, stylish enough for streetwear, and simple enough for beginners to construct successfully.

Understanding Knit Fabrics: The Foundation

How Knits Differ from Wovens

• Stretch: knit fabrics stretch in at least one direction; woven fabrics have minimal stretch on the straight or cross grain
• Recovery: knits return to their original shape after stretching — this is what allows knit garments to maintain their shape through wear
• Seam behavior: knit seams must stretch with the fabric — a regular straight stitch will pop; use a stretch stitch, zigzag, or serger
• Ease: knit garments can be cut with less ease than woven garments, or with negative ease (smaller than the body measurement)
• Fraying: most knit fabrics do not fray — raw edges can often be left unfinished or simply serged

Stretch Percentage: The Most Important Measurement

To measure stretch percentage: cut a 4-inch piece of fabric on the crosswise grain. Stretch it as far as it comfortably goes and measure the stretched length. Calculate: (stretched length – 4) ÷ 4 × 100 = stretch percentage.

• 25% stretch (stable knit): stretches from 4” to 5” — treat almost like a woven; examples: ponte, double knit
• 50% stretch (moderate knit): stretches from 4” to 6” — most common for sweatshirt fabrics; examples: French terry, sweatshirt fleece, jersey
• 75% stretch (stretchy knit): stretches from 4” to 7” — examples: velour, some jerseys
• 100%+ stretch (super stretch): stretches from 4” to 8”+ — used for activewear and swimwear

Best Fabrics for This Design

• Sweatshirt fleece: the classic choice — soft, warm, and easy to sew; the looped back gives it its characteristic texture
• French terry: lighter than sweatshirt fleece with a looped back and smooth face — more breathable and drapey
• Velour: soft, plush, and luxurious — slightly more challenging to sew because the pile can shift during construction
• Jersey knit: the most versatile knit fabric — smooth on both sides, available in many weights
• Brushed fleece: very soft and warm — slightly more difficult to sew because the brushed surface can catch on the presser foot

Understanding the Fit: Ease in Knit Garments

• Positive ease: the garment is larger than the body — fabric hangs away from the body; creates the oversized, relaxed look of a sweatshirt
• Negative ease: the garment is smaller than the body — fabric stretches to fit; used in fitted knit garments like T-shirts and activewear

This sweatshirt uses significant positive ease — the 5-inch side extension and 4-inch shoulder drop create a garment much larger than the body. The bands at the hem and cuffs draw the garment in slightly at the edges, creating the characteristic sweatshirt silhouette: loose through the body, gathered at the hem and wrists.

Part 1: Front Pattern

Step 1: Start with a Shirt Pattern

Use your shirt front, back, and sleeve. Remove seam allowances first so you’re working with the clean base shape. Ignore the button extension and facing — sweatshirts are cut on fold with no opening, so use the center front as the fold line.

Step 2: Lower the Neckline

Lower the center front neckline by ~2 inches (5 cm) and blend smoothly to the shoulder. This creates enough room for the tube neckline to sit comfortably and gives the sweatshirt its characteristic relaxed, casual look. Use a French curve to draw the curve and check it from multiple angles before finalizing.

Step 3: Extend the Length

Choose one option:

• Measure down ~21 inches (53 cm) from the shoulder, or
• Drop the waistline by ~3½ inches (9 cm)

Step 4: Add Width at the Waist

Extend the side seam outward ~5 inches (12.7 cm). This adds 10 inches total to the body circumference (5 inches on each side seam, front and back), creating a very relaxed, oversized fit. For a less oversized fit, reduce to 2–3 inches. For an extremely oversized fit, increase to 6–8 inches.

Step 5: Raise the Underarm Point

From the new waist point, measure up ~6½ inches (16.5 cm) to define the new armhole base.

Step 6: Create a Dropped Shoulder

Drop the shoulder point ~4 inches (10 cm). This is key for that relaxed sweatshirt look:

• A standard shoulder seam sits on top of the shoulder point. A dropped shoulder seam sits 4 inches further down the arm, on the upper arm.
• Creates a wider, more relaxed silhouette across the shoulders and chest
• Simplifies sleeve construction — a dropped shoulder sleeve has a much flatter cap, meaning less easing and a much easier sewing process
• The sleeve seam sits further down the arm where there is more room, making the sweatshirt more comfortable

Step 7: Redraw the Armhole

Connect the new shoulder point to the underarm point. The result is a wider, deeper, more relaxed armhole — almost a straight diagonal line from the dropped shoulder point to the underarm point, with just a slight curve at the underarm.

Step 8: Add Seam Allowances

• Serger: ~⅜ inch (1 cm)
• Regular machine: ~⅝ inch (1.6 cm)

Center front remains on fold. Use consistent seam allowances throughout.

Part 2: Back Pattern

Step 1: Copy Front Shape

Use the front pattern as your base. The back of a sweatshirt is almost identical to the front — the only differences are the neckline height and sometimes the length.

Step 2: Raise Center Back Neckline

Raise the CB neckline ~1¼ inches (3.2 cm) to prevent the neckline from pulling backward. The back of the neck is higher than the front — if the back neckline is the same height as the front, the neckline will pull backward during wear, making the front neckline ride up and the back neckline dig into the neck.

Step 3: Redraw Neckline Curve

Blend smoothly from CB to shoulder using a French curve. The back neckline curve should be shallower than the front. Check that the front and back necklines meet smoothly at the shoulder seam before finalizing.

Part 3: Sleeve Design

Understanding the Dropped Shoulder Sleeve

A dropped shoulder sleeve has a low, flat cap that drops straight into a wide, relaxed armhole — much easier to sew than a set-in sleeve. There is no easing required, and the sleeve can be attached flat (before closing the side seams) for maximum ease of construction.

Step 1: Lower the Sleeve Cap

Drop the sleeve cap ~2 inches (5 cm) to flatten the sleeve. For a dropped shoulder sweatshirt, you want minimal cap ease — ideally zero, so the sleeve lies completely flat when attached.

Step 2: Widen the Sleeve

Add 3–5 inches (9.5–12 cm) total width. After widening, measure the sleeve cap and compare it to the armhole measurement — they should match within ¼ inch.

Step 3: Set Sleeve Length

Minimum ~17½ inches (44.5 cm) — adjust depending on style. Measure from the dropped shoulder point (not the natural shoulder) to the wrist to get the correct sleeve length for this design.

Step 4: Set Sleeve Hem Width

About 14 inches (35.6 cm). Connect underarm to hem with a gentle curve. The cuff will draw the hem in further, so the finished wrist opening will be smaller than 14 inches.

Step 5: Add Seam Allowances

Same as the bodice. Mark the grainline running vertically through the center of the sleeve, parallel to the center fold line.

Part 4: Tube Neckline (Key Design Feature)

Instead of a flat ribbed band, you create a soft, padded tube for the neckline — the signature detail that distinguishes this sweatshirt from a standard design. The tube neckline is softer and more sculptural than a ribbed band, sitting away from the neck slightly and creating a rounded, three-dimensional neckline.

Why a Tube Instead of a Ribbed Band?

• Wider than a standard neckband (5 inches vs. 1–2 inches for a ribbed band) — a more substantial, visible neckline detail
• Can be filled with polyfill or batting to create a rounded, cushioned shape that stands away from the neck
• Creates a softer, more fashion-forward look than a standard ribbed band
• Constructed as a loop (like a cuff) rather than a flat band, giving it its characteristic rounded shape

Step 1: Measure the Neckline

Measure the full neckline (front + back) along the seamline, not the cut edge. A tube that is too short will pull the neckline tight; a tube that is too long will create excess fabric that bunches at the neckline.

Step 2: Draft the Tube

• Length: neckline measurement (the tube is cut to match the neckline, not shorter like a ribbed band)
• Width: ~5 inches (12.7 cm) — creates a finished tube of approximately 2.5 inches when folded in half, minus seam allowances

Cut the tube on the crosswise grain of the fabric so it has maximum stretch.

Optional: Add Soft Filling

Fill with polyfill or batting for a rounded, cushioned, high-end look. Insert after the tube is sewn into a loop and before it is attached to the neckline. Use a small amount — just enough to give the tube a rounded shape without making it stiff or bulky.

Attaching the Tube Neckline

1. Sew the tube into a loop (join the short ends)
2. Fold the loop in half lengthwise (wrong sides together) and press lightly
3. Insert filling if desired
4. Divide the tube loop into quarters and mark with pins
5. Divide the neckline into quarters and mark with pins
6. Match the quarter marks and pin the tube to the neckline, raw edges together
7. Sew with a stretch stitch or serger, stretching the neckline slightly to match the tube as you sew
8. Press the seam allowance toward the garment body (away from the tube)

Part 5: Cuffs & Hem Bands

Understanding Bands in Knit Garments

Bands finish the raw edges and draw the garment in at the hem and wrists. For bands to work correctly, they must be cut slightly shorter than the opening they are attached to — the band stretches to fit the opening, and when it recovers, it draws the fabric in.

Cuffs

• Finished width: ~4 inches (10 cm)
• Cut double width: ~8 inches (20 cm)
• Length: wrist measurement, cut slightly smaller for stretch — typically 80–90% of the wrist circumference

Hem Band

• Finished width: ~5 inches (12.7 cm)
• Cut double width: ~10 inches (25 cm)
• Length: waist measurement, cut slightly smaller — typically 90–95% of the waist circumference

Part 6: Construction

Machine Settings for Knit Fabrics

• Needle: use a ballpoint or stretch needle (size 75/11 or 90/14) — pushes between fabric loops rather than piercing them, preventing skipped stitches and runs
• Stitch: use a stretch stitch, narrow zigzag (1.5–2mm wide, 2.5–3mm long), or a serger — never use a regular straight stitch on knit seams
• Tension: reduce the upper tension slightly to prevent the seam from puckering when stretched
• Presser foot: use a walking foot if available — feeds the top and bottom layers at the same rate, preventing the top layer from stretching more than the bottom

Step 1: Add Front Design (Optional)

Decorate with appliqué, piping, embroidery, or fabric shapes before assembly. Always easier to add surface decoration to a flat piece of fabric than to a constructed garment.

Step 2: Sew Shoulders

Join front and back at the shoulder seams. Press the seam allowance toward the back. Press gently — too much heat or pressure can stretch the seam out of shape.

Step 3: Attach Sleeves Flat

Sew sleeves to armholes before closing side seams — the flat method is much easier with knit garments. Open the garment flat, pin the sleeve to the armhole matching the center of the sleeve cap to the shoulder seam, and sew. No gathering or easing required.

Step 4: Sew Side & Underarm Seams

Sew as one continuous seam — start at the hem, sew up the side seam, pivot at the underarm, and continue down the sleeve to the cuff. This creates a strong, continuous seam with no weak points at the underarm.

Step 5: Attach Cuffs

Sew cuffs into loops, fold in half lengthwise (wrong sides together), and attach to sleeve ends. Divide both the cuff loop and the sleeve hem into quarters and match the quarter marks before pinning. Stretch the cuff to fit the sleeve hem as you sew.

Step 6: Attach Hem Band

Same method as cuffs. Divide both the hem band loop and the sweatshirt hem into quarters and match before pinning.

Step 7: Create the Neck Tube

Sew into a loop, fold in half lengthwise, and add filling if desired. Press the fold lightly — do not press too firmly or you will flatten the tube and lose the rounded shape.

Step 8: Attach Neckline

Match center front, center back, and side midpoints to ensure even distribution around the neckline. Sew with a stretch stitch or serger, stretching the neckline slightly as you sew to match the tube.

Sewing Knits Without a Serger

• Use a stretch stitch: the lightning bolt or triple stretch stitch creates a seam that stretches without popping
• Use a narrow zigzag: set to 1.5–2mm wide and 2.5–3mm long
• Finish raw edges with a zigzag: sew along the raw edge of each seam allowance to prevent curling
• Use a walking foot: prevents the top layer from stretching more than the bottom
• Sew slowly: sewing too fast can cause the fabric to stretch unevenly under the presser foot

Design Variations to Try

• Neckline style: plain tube (no filling), stuffed tube (with polyfill), or decorative stitching on the tube for a quilted effect
• Fit: oversized (more width extension) or slim (reduce side extension to 2–3 inches)
• Sleeve style: extra wide, cropped (shorten to elbow length), or balloon with a tighter cuff
• Fabric mixing: contrast cuffs or hem band in a different color or texture — a classic sweatshirt detail
• Hoodie variation: add a hood instead of the tube neckline — draft the hood as two curved panels that join at the center back
• Cropped sweatshirt: shorten the body to 14–16 inches from the shoulder and eliminate the hem band
• Zip-front variation: add a center front seam and a zipper opening — the tube neckline becomes a collar that frames the zipper

Common Mistakes (and Fixes)

• Neckline too tight: increase tube length — the tube should match the neckline measurement exactly, not be cut shorter like a ribbed band
• Sleeve doesn’t fit armhole: recheck measurements — measure the sleeve cap and armhole and adjust the sleeve width until they match
• Garment feels stiff: use a softer knit with more stretch — the fabric choice is the most important factor in how the finished sweatshirt feels
• Bands too loose: reduce band length — cuffs should be 80–90% of the opening measurement; hem band should be 90–95%
• Seams popping: you used a regular straight stitch — switch to a stretch stitch, zigzag, or serger for all knit seams
• Wavy seams: the fabric stretched during sewing — use a walking foot and sew at a slower speed
• Tube neckline uneven: the quarter marks were not matched before sewing — always divide both the tube and the neckline into quarters and match the marks before pinning
• Garment shrank after washing: the fabric was not pre-washed — always pre-wash knit fabrics before cutting

The Big Picture

Once you understand this, you can design hoodies, drop-shoulder tops, oversized knit dresses, and lounge sets. The principles are always the same: choose a fabric with the right stretch percentage, add positive ease for a relaxed fit, flatten the sleeve cap for easy construction, and finish edges with bands that draw the garment in at the hem and wrists.