This Was a Pair of Sweatpants. Now It’s a Tube Top + Arm Warmer Set — Step-by-Step DIY Tutorial

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Looking to upcycle an old pair of sweatpants into a chic, cozy tube top and matching arm warmers?

You’re in the right place. This beginner-friendly DIY turns soft knit sweatpant fabric into a comfy, street-style two-piece with minimal sewing.

Below you’ll find a clear materials list, precise measurements and a step-by-step tutorial so you can make a flattering, wearable set from a single garment.

What you’ll need

• One pair of stretch sweatpants (preferably medium-weight cotton/polyester knit)
• Measuring tape and fabric chalk or marker
• Sharp fabric scissors
• Safety pins or sewing clips
• Thread and needle or a sewing machine (stretch/ballpoint needle recommended) — optional fabric glue for no-sew finish
• 1/2″ elastic (optional, for top support)
• Optional: serger or zigzag stitch for neatening edges

Before you start: measure for fit

1. Bust circumference: measure around the fullest part of your bust. For a snug tube top, subtract 2–4 inches for negative ease depending on how tight you want it.
2. Top length: decide where you want the tube top to sit (above the bust to midriff). Measure from your underbust (or desired top edge) down to where the top should end. Add 1–1.5 inches for hem/elastic casing.
3. Arm warmer length: measure from wrist up to mid-forearm or elbow, depending on your preference, and add 1/2 inch hem allowance.

Record these numbers. You’ll compare them to the piece you cut from the sweatpants.

DIY Tutorial: Sweatpants into Tube Top + Arm Warmer Set

Step 1 — Deconstruct the sweatpants

1. Lay the sweatpants flat and smooth out seams. You’ll use the waistband and upper legs for the tube top and the lower legs for the arm warmers.
2. Cut across the legs at the point where the crotch seam ends so the top portion separates from the pant legs. Keep the waistband attached to the top portion — this often becomes the top edge of your tube top.

Tip: A jogger style with a good stretch works best. If your waistband is ribbed and snug, it can double as a built-in top edge.

Step 2 — Create the tube top body

1. With the top portion (waistband + upper pant) folded, measure the circumference. If it’s wider than your bust measurement (including negative ease), you’ll need to take in seams. If it’s too narrow, you can add fabric panels or use the other pant leg as a gusset.
2. To make a clean top edge, fold the existing waistband over and try it on. If it’s too loose, remove the waistband seam and replace it with a shorter elastic casing (see Step 4). If the waist rib is the right width, you can leave it as the top edge.

Step 3 — Shape and hem the bottom

1. Mark the desired length of the tube top on the fabric (use your measured top length). Add 1 inch for hem.
2. Cut straight across. Turn the raw edge under 1/2″ and stitch with a stretch stitch or zigzag, or use fabric glue for a no-sew option. If you prefer a gathered waistline, make a small elastic casing and insert 1/2″ elastic to cinch.

Step 4 — Add support: optional elastic casing

If you want extra grip so the tube top won’t slip:

1. Fold the top edge down 1 to 1.25 inches to form a casing (wide enough for your elastic). Pin and stitch around, leaving a 1.5″ gap to insert elastic.
2. Attach a safety pin to the elastic and thread it through, overlap the ends and sew securely. Close the casing gap.

Step 5 — Make the arm warmers

1. Take the lower pant legs and cut off the ankle cuffs if they’re bulky. Flatten one leg and decide the width (usually 6–8 inches for a snug forearm warmer). Cut a rectangle matching your arm length measurement + 1/2″ hem allowance.
2. Fold the rectangle wrong sides together and stitch the long edge with a stretch stitch to form a tube. Hem both openings or use the original cuff as one finished edge.
3. For a thumb hole: cut a small horizontal slit (about 1″–1.5″) near one edge, fold the raw edges under and stitch to reinforce.

No-sew option: Use fabric glue to secure seams and hems—press until dry.

Step 6 — Finishing touches & fit tweaks

• Try the set on. Take in side seams a little if the tube top is too loose, using vertical seams under the arms or along the side.
• Topstitch around the hem or add a decorative band. Adding a slight A-line flare is as simple as trimming the bottom into a gentle curve.
• Wash and dry once to let fabric relax — then final-check the fit.

Styling ideas

• Wear the tube top + arm warmers set alone for festival or layered under a blazer for city cool.
• Pair with high-waisted jeans for balance, or add a chunky belt for structure.
• Try contrasting colors: a dark sweatpant body with lighter rib cuffs makes a modern color-block look.

Troubleshooting

• Tube top slips: add silicone grip tape inside the top edge or tighten with elastic.
• Arm warmers too loose: fold in hem and topstitch or add a hidden elastic channel.
• Fraying edges on thin knits: use a zigzag stitch or fray-check.

Final notes

Upcycling sweatpants into a tube top and arm warmers is an eco-friendly, budget-friendly way to refresh your wardrobe. Because you’re working with stretch fabrics, small fit tweaks go a long way.

This project is perfect for beginners and lets you experiment with no-sew or machine-sewn finishes.

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