Casio Watch Strap Size by Model

Casio is a strange brand to buy straps for: the classic digitals are the cheapest, easiest strap swap in watches, the Duro diver is a normal 22mm diver, and the G-Shocks, the line most people own, do not take standard straps at all. This page gives the strap width between the lugs for the Casio models people search for, with the proprietary-attachment warnings where they apply. Every row is confirmed by two independent sources.

The one-line answer: the square digitals (F-91W, A158, A168, AE1200 Royale, B640W) all take 18mm straps on standard spring bars, the Duro MDV106 takes 22mm, the analog Edifice line runs 20 to 22mm, and G-Shocks take no standard strap at all, only model-specific resin bands and adapters.

Casio strap width by model line

Model lineCaseStrap sizeAttachment
F-91W (and F-84, F-94, F-105, F-108)35mm18mmStandard spring bars
A158WA / A159 (vintage steel)33-35mm18mmStandard spring bars
A168WA (Illuminator)37mm18mmStandard spring bars
AE1200 / AE1300 ("Royale" and siblings)42mm18mmStandard spring bars
B640W (Vintage Edgy)35mm18mmStandard spring bars
CA53W Databank calculator38mm20mmStandard spring bars
CA-56 calculator36mm17mmStandard spring bars
AQ-230 ana-digi (all colorways)30mm18mmStandard spring bars
MTP-1374 chrono (D steel / L leather)44mm22mmStandard spring bars
Duro MDV106 (all colorways)44mm22mmStandard spring bars
Edifice EF-527D and sport chronographs42-45mm22mmStandard spring bars
Wave Ceptor LCW-M170TD40mm20mmStandard spring bars
MTP / LTP analog dress linevaries18 / 20 / 22mmStandard spring bars, by reference
G-Shock DW5600 (square)43mmno standard lugProprietary integrated resin
G-Shock GA-2100 (CasiOak)45.4mm16mm proprietaryIntegrated; adapters allow some 22mm straps
G-Shock GA100 / GA140 line51-55mm18 / 20mm proprietaryProprietary integrated resin

The 18mm square family, and the resin trap

The F-91W's 18mm lug width is confirmed by Casio's official specifications and shared across the whole square-digital family: A158WA, A168WA, AE1200, AE1300, B640W, and the F-84 through F-108 siblings. Any standard 18mm strap fits on the watch's own spring bars, which is why the F-91W has an entire internet subculture devoted to putting it on nylon and mesh. The trap is buying Casio's own replacement strap by width alone: the OEM F-91W resin band (Casio part 71604002) is a 22mm-wide no-straight-mount part fixed with pins, shaped for that case only. Aftermarket standard 18mm straps are the simpler path, reusing the original spring bars.

On the B640W, note the difference between the watch's fitting and its stock bracelet: dealer spec sheets list an 18mm lug width but a 20mm band width, because the stock bracelet's first link overhangs the lugs. An 18mm strap is the correct replacement; a 20mm strap will not fit between the lugs.

The 17mm oddball and the small ana-digi

Two small Casios generate most of the wrong-width returns. The CA-56 calculator watch is a 17mm lug, not the 20mm of its bigger CA53W sibling: Casio's own replacement strap for the CA-56 (part 71604978, shared with the LDF40) is built for a 17mm fitting, and official dealer spec sheets list lug width 17mm for that part. That makes it one of the few current Casios on an odd width, so 17mm straps are the search, not a squeezed-in 18mm. The AQ-230 ana-digi family is the opposite case: it looks proprietary but is a normal 18mm lug on standard spring bars with a straight mount, confirmed on dealer spec sheets for the AQ-230EGG and AQ-230GA variants, so any standard 18mm strap or bracelet fits once the stock band comes off its pins.

On the MTP-1374 chronograph (the D steel-bracelet and L leather variants share the case), the correct width is 22mm. Retailer spec tables carry 22mm band width for the MTP-1374D and the aftermarket builds its curved-end replacement bands for this model in 22mm specifically. The one figure Casio's own spec page prints is wrist fit, 150 to 205mm, not band width, so the 22mm rests on dealer and strap-maker agreement rather than a manufacturer number.

The Duro, and the 20mm myth

The MDV106 Duro is listed at 20mm on some retail pages. It is 22mm. Caliper measurements and independent reviews agree: 22mm lugs, standard spring bars, 44mm case, roughly 48.5 to 49mm lug-to-lug. Buy 22mm; it is also the best-stocked width in the strap market, so the Duro is one of the easiest divers to re-strap at any budget. For whether the 44mm case suits your wrist, that is the separate case size by wrist question.

G-Shocks: why there is no width to look up

Most G-Shocks have no conventional lug gap at all: the resin band is integrated into the case with a proprietary slide-and-click or bolted attachment, so a standard strap has nothing to attach to. The widths quoted in retailer tables (a DW5600's band is roughly 24mm at the case, a GA-2100's connector is 16mm) describe the proprietary part, not a standard lug width. Third-party adapters exist for popular references like the GA-2100 and open the door to standard 22mm straps, but that is a per-reference parts question. The Casio model number on the caseback, and the parts lookup built on it, is the only reliable route for G-Shock band replacement.

Finding your own number if the table misses it

Casio prints the module and model number on the caseback, which is what retailer fitment pages index by. If your reference is missing above, measure the inside gap between the lugs: the method is in the measuring guide, and the lug width chart explains what the number means for shopping. The watch database carries the Duro's and CasiOak's case dimensions if you need those too. For the other big Japanese brands, see the Seiko band size chart (watch for Seiko's fat spring bars on divers) and the Citizen band size chart. For Bulova, Citizen's own subsidiary, the Bulova band size chart carries the per-model widths.

Related guides

Once you know the width: watch band materials compared for what to buy, strap length by wrist so it fits around the wrist and not just the lugs, and how to adjust a watch band, whose Casio section covers the collar pins and clasp-hole tricks these bracelets use. Changing the strap itself is a spring bar job: the spring bar tool guide covers the tool, and spring bar sizes the pins. Also here: the Timex band size chart, the Invicta band size chart, and the watch strap taper chart.

Sources