The verdict, firstCyril Favre

Choose the 35mm for a compact, vintage-leaning fit; choose the 40mm if a bolder case and dial are the reason you want a PRX at all — either way, judge it by wearing span, not the 5mm gap in diameter.

The two blue-dial Powermatic 80 references share a movement, a price and a case thickness on paper, so the real decision is proportion, not spec. Tissot's diameter figures also understate the difference: the PRX's first bracelet links are rigid and don't articulate, so an independent face-to-face review found the true wearing span runs to about 44.9mm on the 35mm and 51.5mm on the 40mm once those links are counted — a wider gap than 5mm suggests.

Try both from above and side-on before deciding. If the 40mm's fixed first links still run flat past the edge of your wrist before the bracelet turns downward, tightening the bracelet will not fix that — the fix is either the 35mm, or the 40mm worn on its rubber or leather strap instead of steel.

Tissot · ~$840PRX Powermatic 80 35mm

Tissot · ~$840PRX Powermatic 80 40mm

The other case

The 40mm is not just the PRX for wrists that can handle it. Its dial gives the waffle-textured pattern, the indices and the Tissot logo more room to read clearly, and it is the size with the widest choice of dial colours and the option of rubber or leather straps — a real escape hatch if the rigid bracelet links overhang your wrist. It also hides its own thickness better than the 35mm does.

Where it is decided

4 arguments

Bracelet span and articulation

Tissot's diameter and case-length figures don't describe what actually crosses your wrist, because the first bracelet links are rigid and don't articulate. A third-party face-to-face review measured the true wearing span, links included, at roughly 44.9mm on the 35mm and 51.5mm on the 40mm — case-only, about 38.5mm and 44–45mm. The 35mm's bracelet is also proportionally narrower, tapering 24mm to 16mm against 27mm to 18mm on the 40mm. If the 40mm's first links overhang the flat top of your wrist, sizing the bracelet down won't remove them — you either move to the 35mm or put the 40mm on rubber or leather instead of steel.

Goes to

Tissot PRX Powermatic 80 35mm

≈44.9mm span (35mm case)
≈51.5mm span (40mm case)

Dial presence and proportions

The 40mm's extra room around the tapisserie pattern, indices and logo reads as the more balanced dial to at least one independent reviewer, who nonetheless preferred the 35mm's date window sitting closer to the dial's edge. Neither reading is wrong — one wants the PRX noticed first, the other wants a quieter face — but the difference between the two dials is real and worth judging in person rather than assuming it simply scales with the 5mm of diameter.

Goes to

Draw

35mm dial, date near edge
40mm dial, more open layout

Thickness and side profile

Tissot lists both cases at an identical 10.93mm thick, so the two sizes are equally slim on paper — a third-party measurement nearer 11.3mm is a measurement-method variance, not a contradiction. The two don't look equally thin in the metal: the same height reads deeper on the smaller 35mm case and flatter across the broader 40mm face, and Tissot sinks much of that height into the caseback on both sizes, which softens the effect either way. Judge the side profile in person, and don't expect the 35mm to look slimmer just because it measures smaller.

Goes to

Draw

35mm — 10.93mm thick, reads deeper
40mm — 10.93mm thick, reads flatter

Substance and price

Both references run the same automatic Powermatic 80 calibre with up to 80 hours of reserve, plus a date, sapphire crystal, a see-through caseback, a quick-release steel bracelet and 100m water resistance — and both list at the same price; Tissot lists the 40mm heavier on the bracelet, 138g against 104g for the 35mm. On specification they are one watch in two proportions, so a size that fits poorly is not “the better watch” just because it is bigger or feels newer; buy the one that actually sits right on your wrist.

Goes to

Draw

35mm — 104g listed, same price
40mm — 138g listed, same price

Who should buy which

Tissot PRX Powermatic 80 35mm

You want the PRX to read as compact and closer to its 1970s original proportions
Your wrist is on the smaller side, or you'd rather not risk the 40mm's rigid links overhanging its edge
You prefer a quieter dial, with the date sitting close to the edge rather than centred in open space
You're choosing on proportion alone — the movement, price and water resistance are identical either way

See the PRX Powermatic 80 35mm

Tissot PRX Powermatic 80 40mm

You want the broadest, most assertive read of the PRX's 1970s sports-watch design
You want the widest choice of dial colours, and the option to swap onto rubber or leather
You'd rather have the tapisserie pattern and indices given more room to read
Your wrist can carry the ≈51.5mm effective span without the first links overhanging its edge

See the PRX Powermatic 80 40mm

Your personal verdict

Wrist shape and the flat-top width of your wrist usually decide this pair more reliably than the editorial verdict — try both on a properly sized bracelet before you commit.

Find your PRX size

Explore the PRX Powermatic 80 dial range

The 35mm and 40mm Powermatic 80 share much of the same dial-colour catalogue on the steel bracelet — compare the full range before deciding on a size.

PRX Powermatic 80 — 35mm dials

PRX Powermatic 80 — 40mm dials

Frequently asked

Does the PRX Powermatic 80 40mm wear like an ordinary 40mm watch?

No. Its rigid first bracelet links push the effective wearing span to about 51.5mm, closer to some conventional 42mm watches. Compare that span against the flat top of your wrist rather than trusting the 40mm diameter on its own.

Is the 35mm a lesser watch — thinner, smaller movement, less water resistance?

No. Both blue-dial references share the same official 10.93mm thickness, the same Powermatic 80 calibre with up to 80 hours of reserve, sapphire crystal, a see-through caseback and 100m water resistance. The 35mm's only real difference is a lighter, narrower bracelet.

Which size should I buy for a small wrist?

There's no reliable wrist-circumference cutoff. If the 40mm's first links overhang the flat top of your wrist, the 35mm is the safer starting point; if those links start turning downward before they reach the edge, the 40mm stays an option even on a modest wrist. Try both on a properly sized bracelet before deciding.

Is the PRX Powermatic 80 available in other sizes besides 35mm and 40mm?

Yes. Tissot also catalogues a 38mm PRX in titanium and Damascus steel, and a 42mm PRX Chronograph on an automatic Valjoux movement, alongside quartz PRX models at 25mm and 35mm. This page compares only the two standard steel automatic sizes; the 38mm titanium decision is a separate one.

Does bracelet sizing change how the PRX wears?

It changes comfort, not the rigid first links themselves. Removing links tightens the bracelet around your wrist, but the first two links stay fixed and flat regardless of adjustment — that rigid section is what decides whether a size overhangs your wrist, not how tightly the rest of the bracelet is sized.