Am I Size M or L? A No-Nonsense Guide to UK/US Charts, Measurements & Fit

You can be an M in one brand and an L in another-on the same day. The trick isn’t guessing; it’s measuring once, mapping properly, and adjusting for fabric and fit. In two minutes, you can answer the exact question you came for: am I size M or L-for this item, from this brand, with the fit I want?

TL;DR

• Measure your bust/chest and waist (and hips for bottoms) snug but not tight. Write them down in cm and inches.
• Compare to the brand’s size chart. If you’re between M and L, choose based on fabric and fit: stretch or relaxed fit → M; rigid fabric or tailored fit → L.
• Heuristic: Women’s M ≈ Bust 92-97 cm, Waist 74-79 cm; L ≈ Bust 98-104 cm, Waist 80-86 cm. Men’s M ≈ Chest 97-102 cm, Waist 81-86 cm; L ≈ Chest 103-108 cm, Waist 89-94 cm.
• Layering a jumper/coat? Size up. Want a fitted look? Stay with the smaller of your two sizes.
• When in doubt, measure a favourite garment flat and match the product’s garment measurements.

Measure, map, decide: the two‑minute method

Letter sizes aren’t standard. That’s not your body-it’s the industry. UK high street brands cut differently to US mall labels; athletic brands cut differently to designers. Bodies vary, too. So, skip the guesswork and use this fast method.

Step 1: measure the right bits

1. Bust/Chest: Wrap the tape around the fullest part, level across the back. Breathe out normally. Note cm and inches.
2. Waist: Find your natural waist (the crease when you bend to the side). Keep the tape snug, not tight.
3. Hips (for bottoms/dresses): Around the fullest part of your bum.
4. Shoulders (if you have broad shoulders or are buying tailored tops/coats): Shoulder tip to shoulder tip across the back, or measure a shirt that fits.
5. Inseam (for trousers): Crotch seam to hem on trousers that fit how you like.

Pro tip: If the brand lists garment measurements (e.g., chest width laid flat), measure a similar piece you already own laid flat. Compare like-for-like. This bypasses vanity sizing and inconsistent charts entirely.

Step 2: map to the brand’s size chart

• Use the brand’s chart first, not a generic one. Many brands now publish body and garment measurements. If they share both, use garment measurements for accuracy.
• If you can’t find the chart, use the cheat table below as a starting point, then adjust for fabric and desired fit.

Step 3: choose your size using ease and fabric

• Ease = the difference between your body measurement and the garment. Different items need different ease.
• Typical ease ranges (body to garment):

• T‑shirts/jersey tops: +4-8 cm chest (1.5-3 in)
• Sweaters/hoodies: +10-15 cm chest (4-6 in)
• Tailored shirts/blouses: +8-12 cm chest (3-5 in)
• Jeans/trousers (woven): 0-2 cm waist (0-0.75 in)
• Leggings (stretch): −2 to −10 cm waist/hip (negative ease)

Fabric rule of thumb:

• Stretchy knit, elastane blend, or “relaxed fit”: you can go with the smaller of the two sizes if you’re between M and L.
• Rigid woven, tailored, or lined: go with the larger size if you’re between.
• Linen and raw denim often relax with wear; structured suiting and coats don’t.

Fit goal matters

• Fitted/clean: choose the smaller size, but check chest/hip ease from the list above.
• Regular: go with the size that matches most of your body measurements (see the 80% rule below).
• Oversized: choose the larger size or look for an oversized cut in your usual size.
• Layering a jumper under a blazer or coat? Size up.

Two decision heuristics

• 80% rule: If 2 out of 3 of your key measurements (bust/chest, waist, hips) fall into M, pick M-unless the item is rigid and tailored. If they fall into L, pick L-unless it’s stretchy.
• Closest critical fit: Prioritise the measurement most likely to pull. Tops and dresses: bust/chest and shoulders. Bottoms: hips (for skinny/straight) or waist (for high-waisted tailored). If that critical measure falls in L, choose L.

What the letters usually mean (body measurements)

• Women’s M: Bust ≈ 92-97 cm (36-38 in), Waist ≈ 74-79 cm (29-31 in), Hips ≈ 98-103 cm (38.5-40.5 in)
• Women’s L: Bust ≈ 98-104 cm (38.5-41 in), Waist ≈ 80-86 cm (31.5-34 in), Hips ≈ 104-109 cm (41-43 in)
• Men’s M: Chest ≈ 97-102 cm (38-40 in), Waist ≈ 81-86 cm (32-34 in)
• Men’s L: Chest ≈ 103-108 cm (41-43 in), Waist ≈ 89-94 cm (35-37 in)

Why sizes vary (so you don’t take it personally)

Brands use different fit models and grading rules. ISO 8559-2 and the European EN 13402 give a common language for body measurements, but they don’t force identical patterns. The SizeUK 3D body scan survey showed huge shape differences even at the same bust/waist numbers-especially bust-to-shoulder and waist-to-hip ratios-so two size 12s in different cuts can feel miles apart. Add vanity sizing (documented shifts of ~1-2 sizes since the 1970s in consumer research), and you get the chaos we all know.

Unisex and brand tendencies

• Unisex tees and hoodies are usually based on men’s blocks. Many women prefer to size down one letter for a closer fit, or keep their usual size for relaxed/boxy.
• European fast-fashion often runs slimmer; some US brands run roomier. Performance sportswear can be trim through the shoulders and arms for mobility.

Body shape adjustments

• Full bust or broad shoulders: prioritise chest/shoulders. Size up on tailored tops/coats; you can take in the waist.
• Curvy hips: for rigid jeans/skirts, choose the size that fits hips; tailor the waist.
• Taller frames: watch length (sleeve, torso, rise). A perfect M in width may need a Long length or the L for length.
• Petite frames: choose the right length first. Petite cuts keep proportions (shoulder, rise) sensible.

Real‑world examples, cheat‑sheets, and size charts

Examples make it click. Here are common scenarios with numbers to show how the choice flips depending on fabric and fit.

Scenario 1: Women’s ribbed knit top (stretch)

• Your measurements: Bust 96 cm, Waist 78 cm, Hips 102 cm.
• Brand chart: M bust 92-97, L bust 98-104.
• Choice: M. It’s a stretchy rib; you sit at the top of M, and the fabric has give. Expect a close, flattering fit.

Scenario 2: Women’s woven blouse (no stretch)

• Your measurements: Bust 96 cm, Waist 78 cm. Shoulders slightly broad.
• Brand chart: M bust up to 95, L bust up to 101.
• Choice: L. Woven + broad shoulders = you’ll appreciate the extra ease at bust/shoulders. You can tuck or tailor the waist if needed.

Scenario 3: Men’s sweatshirt (medium weight fleece)

• Your measurements: Chest 103 cm, Waist 86 cm.
• Brand chart: M chest 97-102, L chest 103-108.
• Choice: L. You’re right at 103 cm and want room for a tee underneath.

Scenario 4: Women’s high‑waisted rigid jeans

• Your measurements: Waist 79 cm, Hips 104 cm.
• Brand chart: M hips up to 103, L hips up to 109.
• Choice: L, because hips drive the fit in rigid denim. Belt or tailor the waist.

Scenario 5: Unisex oversized tee

• Your measurements: Chest 97 cm.
• Brand chart (unisex): M chest 97-102, L chest 103-108.
• Choice: M for a relaxed look; L if you want streetwear‑oversized or to style with cycling shorts.

Quick decision cheat‑sheet

• Between sizes? Stretch/jersey → smaller; rigid/tailored → larger.
• Layering? Size up.
• Broad shoulders/full bust? Size up in structured tops; fit the shoulders first.
• Rigid denim/straight skirts? Fit the largest area (usually hips), tailor the rest.
• Want fitted? Choose the smaller size but check ease values.
• Unisex top? If you usually wear women’s sizing, consider sizing down one letter for a regular fit.

Typical M vs L (UK/US/EU) to get you in the right aisle

Use this table as a starting point. Always check the brand’s chart if you can.

How to use that table

• Find your closest match in cm/in. If you hit the top of M or bottom of L, use the fabric and fit rules to decide.
• Between UK and US sizes, remember: roughly, UK size = US size − 2 (e.g., UK 12 ≈ US 8). EU numbers are different and refer to a different scale (e.g., UK 12 ≈ EU 40).

Brand and category notes from the fitting room

• European fast‑fashion often runs slim through shoulders and hips; consider the larger size in woven pieces.
• Outdoor/sports brands can be trim at the shoulders and sleeves; if you lift or row and have strong lats/delts, consider sizing up on jackets.
• Denim: raw or rigid? Fit the hips and seat first. Stretch denim (1-2% elastane) can usually handle the smaller size if you’re between.
• Formal suiting: prioritise shoulders. A size up you can tailor; too‑small shoulders you can’t fix.

Buying online from the UK in 2025

• Returns policies have tightened; some high street brands now charge for postal returns. Keep tags on until you’re sure.
• Order two sizes only if free returns apply or you can use a locker drop to keep costs low.
• Check if the product page lists garment measurements or a fit note (e.g., “runs large”); this often saves a return.

Quick answers, fixes, and next steps

Mini‑FAQ

• Q: My bust is in L, my waist is in M. What now?
  A: For tops and dresses, fit the bust first. Choose L and tailor the waist if needed. For knits or stretchy dresses, you may get away with M if you’re right on the line.
• Q: I’m between sizes on a hoodie. M or L?
  A: If chest is 100-103 cm and you want room, go L. If you want a neat fit, M. Hoodies often have generous ease.
• Q: Do men’s and women’s M/L match?
  A: Not directly. Unisex tees are usually men’s blocks. If you wear a women’s M, a unisex S or M often gives a similar fit. Always check chest width in cm/in.
• Q: Will cotton shrink?
  A: Pre‑shrunk cotton still shrinks a little with hot washes/tumbles. Allow 2-3% shrinkage. Wash cool and air‑dry if you like the fit out of the bag.
• Q: I lift and have big shoulders. Which way should I go?
  A: Prioritise shoulders/chest. Choose the larger letter in woven shirts, blazers, and coats. For tees and hoodies, you can often stick with the smaller letter for a tapered look.
• Q: Pregnant or postpartum-how to choose?
  A: For first/second trimester in stretchy styles, one size up from your pre‑pregnancy letter usually works. For woven or late second/third trimester, two sizes up or dedicated maternity lines are safer.
• Q: Plus size at the border of L/XL?
  A: If the brand tops out at L and you’re at the upper end of L measurements, try their curve/plus range for better proportions. The grading is kinder to curves.

Troubleshooting by scenario

• Broad shoulders but small waist: Size up for shoulders in woven tops, then tailor waist darts or take in side seams.
• Full hips, smaller waist: Choose the size that fits hips in jeans/skirts; a quick dart or waist nip makes it look custom.
• Tall with long arms: Look for Tall/Long options. If none exist, try the larger letter for sleeve length.
• Short torso: Cropped cuts can look regular on you. You may not need to size up for length.
• Between M and L in active leggings: If fabric has 20%+ stretch, take M for support; if light compression or 4‑way stretch is minimal, L feels better.

Next steps (so you nail it the first time)

1. Write down your current measurements in cm and inches. Date them. Bodies change.
2. Check the product page for body vs garment measurements. Prefer garment measurements if available.
3. Decide your fit goal (fitted, regular, oversized). Apply the ease list to sanity‑check.
4. Consider fabric. Stretch or jersey? Lean smaller. Rigid or tailored? Lean larger.
5. Ordering online? If returns are free, order M and L, keep the one that fits. If returns are paid, use garment measurements and your best‑fit piece at home to compare.

Why you can trust this approach

It’s how pattern cutters and fit techs work: measure the body, add appropriate ease, map to a block. Industry standards like ISO 8559‑2 and EN 13402 formalise the body‑measurement language. Brands still make style choices-that’s why a relaxed M tee and a tailored M blouse feel different-but with your numbers, fabric knowledge, and ease rules, you’re making a precise call, not a guess.

One last sanity check

• If your critical measure sits at the very top of M and the piece is woven/structured, choose L.
• If your critical measure sits at the very bottom of L and the piece is stretchy/relaxed, choose M.
• If you’ll wear it over layers or want extra drape, choose L.
• If you want it neat and you’re within the M range, choose M.

Do this once, save the notes in your phone, and the “M or L?” question stops being a coin toss. You’ll buy with intent, your parcels will fit better, and your returns will go down.