The fit sentence belongs to the model
Hermès prints a sentence on individual product pages and not a universal chart, which is why the same question gets different answers across the range. The Oran, Oasis and Chypre use the usual-size or half-size-up wording for a high instep. The Izmir, Oz mule and shearling-lined Lazy loafer ask for half a size up. The Empire sandal is described as running true to size. None of those sentences carries a centimetre figure, and the house's own size-guide page documents enamel bracelets at 62, 65 and 70 mm and belts by the centimetre, with shoes absent altogether. The numbers that do appear belong to the sole: 0.4 inch of heel on the Oran against 0.2 inch front to heel, restated on the China page as 1 cm and 0.5 cm, and 1.2 cm of anatomical rubber under the Chypre. Record the model reference and its fit sentence together before comparing a listing elsewhere.
A French 37 lands on two different American numbers
Four published tables put the same French number against different American ones. Fashionphile prints FR 37 as US 7 and UK 4, and sizedepo repeats that mapping for the Oran, while choozeshoe and sizechartly call EU 37 a US 6. At FR 39 the split widens: one table says US 9, another says US 8, and the centimetre columns attached to that row read 24.7, 25.0 and 25.5 cm. That spread is 0.8 cm, close to a full size on a shoe last, so averaging the sources settles nothing. Measure the longer foot, place it against a centimetre column, and treat the American letter as a cross-check rather than the answer. Then apply the model's own sentence about the instep, because length and last volume are two separate questions with two separate answers. The centimetre column is the only shared ground across the four tables.
Oran and Chypre hold the foot differently
The Oran uses a single-piece calfskin upper with the H cut out and no adjustable fastening. A half size moves the strap across the instep as well as changing footbed length, which is why the high-instep wording appears. The Chypre sits on an anatomic rubber sole and has an adjustable strap. The same half-size instruction still appears, but the strap can absorb some of the volume difference. Neither construction changes the need to measure the longer foot and check where the heel sits inside the footbed.
The insole width matters as much as length
A flat slide has no heel counter, laces or closed sides to hold the foot in place. Width across the forefoot decides whether the sole supports the foot without the toes resting over the edge. Ask for the widest point of the footbed and the clear width of the upper at the instep. The fit sentence addresses length and instep pressure, but it does not describe a wide foot. If the footbed is short, move up a size; if the upper presses while the footbed length is right, compare a different model or strap construction.
Leather, suede and lining change the first feel
Calfskin can soften across the vamp, suede can settle but mark more easily, and a lined or shearling version uses internal volume that a single-layer model does not. The sole also matters: the Oran uses leather; the Chypre uses anatomic rubber. A thicker or more shaped sole changes where the foot sits and how much toe clearance remains. Material does not alter the printed size, but it can make the same footbed feel tighter or looser. Ask for side and top photographs plus a close view of the lining.
The four-slide check
Send the model name, printed EU size, longer foot in centimetres and footbed length. Add forefoot width and instep height where possible. If a seller already owns the pair, ask for a tape inside from heel edge to toe, the full upper width laid flat, and a side view of the sole. Compare the result with the fit sentence on the exact model. This turns photographs of the H cut-out or adjustable strap into a size decision rather than a visual comparison.
Choosing between Oran and Chypre
If the concern is a high instep, Oran's fixed H upper leaves less adjustment than Chypre's strap. The fit sentence for both still points toward half a size up when that area is high, but Chypre can take some variation through the fastening. Compare footbed width and instep clearance as well as length. A strap that can be adjusted does not fix a foot extending beyond the sole, and a longer footbed does not fix a strap pressing on the instep when the foot is narrow.