Being between two sizes is completely ordinary. Each silhouette holds the body in a different place, so the useful question is not “Which letter do I usually wear?” but “Which point must stay secure and comfortable for this dress?” Measure first, read the exact product measurement guidance, then test the decision in the conditions of the event.
Start with measurements, not the label
Measure bust, waist at the stated position and hips over the base layer you plan to wear. Keep the tape level and record the actual centimetres, especially when a number is close to a limit.
Elodie Dress A013 shows why a size label needs context: its over-bust waist notes are under 66 cm for S, under 70 cm for M and under 76 cm for L. The difference is not only four centimetres; it also changes how the bodice, length and overall hold may feel on you.
Find the measurement that decides the fit
A cup or structured bodice may depend most on bust support. Becky Dress A003 in M has the note “V1 under 86”, meaning the bust is the listed reference. A fitted or corset style often makes waist the key point, while a mermaid shape also needs hip space and a natural stride.
If your bust is closer to M and your waist is closer to S, a fixed upper body may make M the more sensible fitting candidate. If your waist is close to M while your bust is within S, a model with the right adjustment construction can be worth trying. A fitting will show whether that choice stays secure and comfortable in movement.
A tie does not replace a fitting
Calliope Dress A004 in M is noted as over-bust waist under 68 cm with a back tie. The tie can refine how the bodice sits, but it does not publish an unlimited adjustment range. Tie it to a stable, breathable position, then sit, walk and lift your arms.
Do not tighten a rental until the fabric wrinkles or your body feels held in. If a slightly roomier size stays stable and lets you breathe naturally, it may be a better event-day choice than a smaller one that only works in front of the mirror.
Decide by the itinerary
For a seated dinner, test normal breathing and sitting for at least ten minutes.
For photos, test the angles in which the neckline and back will be visible.
For stairs, dancing or several locations, take a long step, turn and raise both arms.
Bring the exact shoes, bra and shapewear that you will really use.
Compare two sizes properly
Take front, side and back photos under the same light. Record the model, size and measurement guidance beside each image. Look for stable shoulders, neckline and zip, then check whether the skirt and hem still move easily. Avoid filters: they can hide a pulling bodice or change the perceived colour.
When you cannot try both sizes
Send Rent by Châu the exact model, both candidate sizes, bust, waist and hips in centimetres, the measurement position, your base layer and the event plan. Do not round a number down to fit an “under” limit. A clear message is more useful than guessing from weight or a familiar brand size.
A calm final note
The right choice is the size that allows the dress to stay in place while you live the event. Read how to measure for a dress rental and the dress fitting checklist before making a final decision.
Do not solve the decision with alteration
A dress that only works after pins, tape or an improvised adjustment is not a reliable rental choice. The product’s own closure or tie can be used as the shop instructs, but it should not be stretched beyond its listed measurement guidance. If neither size works in natural movement, compare another silhouette.
Save the result for the event day
After fitting, write the exact model, size, bra, shoes and the reason it won. This prevents a later change of shoe or base layer from quietly undoing the assessment. If your measurements change or the plan changes, check again rather than assuming the original choice still has the same conditions.