Answer with the size your exact product’s information supports, not the size the buyer usually wears. Compare their relevant body measurements and preferred fit with your published chart. If one size matches one measurement but not another, explain the trade-off; suggest a size only when the product’s fit information resolves it. Otherwise, ask the question that would change your recommendation.
Get the measurements and fit preference that matter
Start by identifying the exact garment and variant. For trousers, a waist measurement alone may miss a hip or length issue; for a top, ask about the body dimensions that its chart uses. Confirm the units and whether the buyer wants a close fit, room to move or space for layers. A post that says only “I’m usually a medium” is not enough to pick between your sizes: REI advises using body measurements and the brand’s size chart because size labels vary across brands.
Ask for only what would affect the answer. “Which trousers are you looking at, and what are your waist and hip measurements in inches or centimeters? Do you prefer a close or relaxed fit at the hips?” is more useful than requesting every measurement on the chart. If the buyer has already provided those details, use them rather than asking again.
Compare the buyer with this product’s chart
Check what your chart actually measures before matching numbers. Body-measurement ranges describe the wearer; finished-garment measurements describe the item. Do not treat a 40-inch garment hip as interchangeable with a 40-inch body hip. Read the product’s fit description alongside the chart, including any relevant information about stretch, adjustability, rise or length. If that information is missing, do not fill the gap with an assumption about how the garment will feel.
Compare each relevant dimension, not just whichever one produces an easy answer. If the buyer falls within one size’s waist range and another size’s hip range, neither label settles both concerns. Look for product-specific information that explains the trade-off. If you cannot establish that the preferred size accommodates the other measurement, say what the chart indicates and what remains uncertain.
What to say when waist and hips point to different sizes
Consider this fictional buyer and fictional trousers chart; these are illustrative numbers, not measurements for a real product. The buyer posts: “My waist is 29 inches, hips 41 inches, and I prefer room at the hips. S or M?” Assume the chart gives body-measurement ranges of S: 28–30-inch waist and 38–40-inch hips; M: 30–32-inch waist and 40–42-inch hips. The buyer’s 29-inch waist falls within S, while their 41-inch hips fall within M. S misses the listed hip range, and M misses the listed waist range. The chart alone does not establish that M will feel roomy at the hips or stay comfortable at the waist.
If this fictional product’s additional fit information explicitly confirms that its M waistband adjusts to a 29-inch waist and gives the buyer the hip room they want, you can suggest M conditionally: “For these trousers, your hips fall in M and your waist falls in S. The M’s adjustable waist covers 29 inches, and its fit information indicates the extra hip room you’re after, so I’d start with M. I can’t guarantee how it will feel on you.” Make that recommendation only if your real product information supports both statements.
If the only information available is the fictional chart, do not present that M recommendation as settled. A more accurate reply is: “Your 29-inch waist falls in S, while your 41-inch hips fall in M. Since you want room at the hips, M is the size to investigate, but its listed waist range starts at 30 inches. Is a looser waist acceptable to you, or do you need it to sit closely? I’ll check whether this style has waist adjustment before suggesting a size.” The answer gives the buyer a useful comparison and identifies what must be checked next.
Check the suggested X reply before sending
ReachFast says it reads a seller’s website, finds and ranks relevant public X posts, and prepares a suggested reply that opens in the X thread; the seller chooses whether to send it. For a sizing question, treat that text as a draft, not as a fit check. Compare every measurement, size range and fit claim in it with the exact item’s published information. Remove any promise that a size “will fit,” and answer the buyer’s stated preference rather than repeating a generic size label.
If the post lacks the details needed to make a sizing decision, ask for them instead of guessing. For the separate question of whether a public request is worth answering at all, see how to qualify product recommendation requests on X.
