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Choose the GMA-S160 if a smaller, lighter watch is your priority; choose the GMA-S2100 if you prefer its octagonal design and want more timing functions. In Casio’s specifications for the cited variants, the S160-7A is 31 g and measures 40.7 × 35.7 × 10.8 mm, while the S2100-1A is 41 g and measures 46.2 × 42.9 × 11.2 mm.
Size and weight: the S160 is the more compact choice
Casio’s European product pages list these dimensions and weights for the specific variants below. Other color or model suffixes may have different specifications, so check the page for the exact watch you are considering.
| Specification | GMA-S160-7A | GMA-S2100-1A |
|---|---|---|
| Dimensions (H × W × D) | 40.7 × 35.7 × 10.8 mm | 46.2 × 42.9 × 11.2 mm |
| Weight | 31 g | 41 g |
| Battery | One CR1025 cell | Two SR726W cells |
| Approximate battery life | Approximately 3 years | Approximately 3 years |
Those figures make the S160 the smaller and lighter option on paper. Casio describes its design as compact and slim, saying its component structure lets the module be made “as compact and slim as possible.” That is the manufacturer’s description, not an independent fit test. See Casio’s GMA-S160 series page and the GMA-S160-7A specifications.
Battery life is an estimate rather than a guarantee; actual life depends on use. Casio lists different battery types for these variants, but its product pages do not establish a controlled, real-world comparison of how long they last.
#1 Best Overall
- Shock-Resistant Durability: Built to withstand the toughest conditions, this G-Shock watch features a rugged resin case and bezel, perfect for outdoor adventures and extreme sports.
- 200M Water Resistance: Designed for water enthusiasts, it’s suitable for scuba diving, swimming, and snorkeling, providing reliable protection up to 200 meters.
- Electro-Luminescent Backlight: The blue-green EL backlight with afterglow ensures clear visibility of the time, day, and date, even in complete darkness.
- Precision Stopwatch & Countdown Timer: Measure elapsed and split times with the 1/100-second stopwatch, or set up a countdown timer with up to a 24-hour range, ideal for timing workouts or daily tasks.
- Multi-Alarm with Flash Alert: Stay on schedule with a customizable alarm, hourly chime, and flash alert that combines light and sound for added convenience.
Functions: the S2100 offers a broader timing toolkit
Both watches combine analog and digital displays, but their listed timekeeping functions differ. The S160 provides dual time and a stopwatch that measures elapsed time in 1-second increments. The S2100 has world time for 31 time zones, a stopwatch measuring to 1/100 second with split and 1st–2nd place timing, a countdown timer, and five daily alarms.
| Function | GMA-S160 | GMA-S2100 |
|---|---|---|
| Additional time display | Dual time | World time: 31 time zones |
| Stopwatch | 1-second elapsed-time measurement | 1/100-second measurement; split and 1st–2nd place timing |
| Countdown timer | Not listed on the cited product page | Listed |
| Daily alarms | Not listed on the cited product page | Five |
| Double LED light and hand shift | Both listed | Both listed |
The S2100 is the more useful fit if you expect to use its countdown timer, alarms, world time, or finer stopwatch increments. The S160 still covers dual time and elapsed timing, so its compact size does not mean giving up everyday analog-digital timekeeping. The function details are listed on Casio’s S160-7A page and S2100-1A page.
Rank #2
Design and construction: compact styling versus an octagonal bezel
GMA-S160
The S160’s design emphasis is a compact, slim case. Casio also says key bezel and band resin components use bio-based resin. That material detail may matter if you prefer a watch with some components made from renewable organic resources; it does not change the published size comparison.
GMA-S2100
The S2100 takes the octagonal-bezel look associated with the GA-2100 line into a compact configuration. Casio describes its design as having a flat face, simple bar hour markers, and Carbon Core Guard construction. The octagonal profile is the clearest visual reason to choose it over the S160 if dimensions are not your deciding factor. See Casio’s GMA-S2100-4A product page for that design description.
Rank #3
- Rugged & Sporty Design – Matte black finish with bold digital display, built for tactical, military, and extreme sports enthusiasts.
- High-Brightness LED Backlight – Features Super Illuminator LED with a light guide plate, ensuring exceptional visibility in low-light conditions.
- 200M Water Resistance – Engineered for swimming, snorkeling, and outdoor adventures, this shock-resistant watch is ready for action.
- Extended 7-Year Battery Life – Powered by a CR2025 battery, offering years of reliable performance without frequent replacements.
- Shock-Resistant Structure – Built to withstand extreme conditions, making it ideal for sports, military, and rugged outdoor use.
Durability and water resistance
Casio lists shock resistance and 200-metre water resistance (20 bar) for both cited variants. This is the manufacturer’s rating; it should not be read as a specific dive certification. The specifications also list mineral glass, double LED lighting, and a hand-shift feature for both models. Check the official page for your exact suffix, since the cited measurements and specifications apply to the variants named here.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Which one should you choose?
- Choose the GMA-S160 if lower weight and smaller published dimensions matter most, or if you prefer its compact styling. See the Casio GMA-S160-7A specifications for the cited variant.
- Choose the GMA-S2100 if you want an octagonal bezel and are more likely to use world time, a countdown timer, five alarms, or its more precise stopwatch modes. See the Casio GMA-S2100-1A specifications for the cited variant.
Retail prices, stock, and available colors depend on region and date; the cited specification pages do not establish current availability or pricing. Confirm the model suffix and local listing before buying.
Quick Recap
Best Value
- Step-Tracker
- Bluetooth Enabled
Rank #4
- Iconic G-SHOCK Square Design – The legendary square case that started it all, delivering timeless style and the rugged durability G-SHOCK is known for.
- Shock Resistant & 200M Water Resistant – Built to withstand impacts, swimming, snorkeling, and demanding everyday use.
- Super Illuminator LED Backlight – Bright white LED with afterglow ensures excellent readability in low-light conditions.
- Essential Digital Features – Includes 1/100-second stopwatch, 24-hour countdown timer, multi-function alarm, flash alert, and full auto-calendar.
- Reliable 5-Year Battery Life – Powered by a CR2016 battery for long-lasting performance with minimal maintenance.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
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