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. For the specific variants compared here, Casio lists the GMA-S160-7A at 40.7 × 35.7 × 10.8 mm and 31 g, versus 46.2 × 42.9 × 11.2 mm and 41 g for the GMA-S2100-1A.
How different are their sizes?
The GMA-S160-7A is smaller in every listed dimension and 10 g lighter than the GMA-S2100-1A. The figures below are Casio specifications for these exact regional variants; other color or suffix variants should be checked on their own product pages.
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| Specification | GMA-S160-7A | GMA-S2100-1A |
|---|---|---|
| Dimensions (L × W × H) | 40.7 × 35.7 × 10.8 mm | 46.2 × 42.9 × 11.2 mm |
| Weight | 31 g | 41 g |
| Water resistance | 200 m / 20 bar | 200 m / 20 bar |
| Battery life estimate | Approximately 3 years; use-dependent | Approximately 3 years; use-dependent |
| Battery | One CR1025 | Two SR726W cells |
| Glass | Mineral | Mineral |
Casio describes the GMA-S160 as compact and slim, saying its component structure is optimized to make the module as compact and slim as possible (GMA-S160 series). That is the manufacturer’s design description, not an independent fit assessment. If you have a narrow wrist or want less weight on your arm, its published dimensions make the S160 the more compact choice.
Which one has the more useful functions?
Both are analog-digital watches with shock resistance, double LED lighting, and a hand-shift feature that can move the hands out of the way of the digital display. Their timing and timekeeping options differ:
#1 Best Overall
- Strap: blue plastic with pin buckle
- Casing: plastic blue
- Functions: alarm, lighting, stopwatch, countdown, glow in the dark
- Display: analogue-digital
- Watch glass: mineral glass
| Function | GMA-S160 | GMA-S2100 |
|---|---|---|
| Additional time display | Dual time | World time across 31 time zones |
| Stopwatch | 1-second elapsed-time stopwatch | 1/100-second stopwatch, with split and 1st–2nd place timing |
| Countdown timer | Not listed on the cited product specifications | Listed |
| Daily alarms | Not listed on the cited product specifications | Five |
For basic elapsed-time tracking and a second time display, the S160 covers the stated essentials. The S2100 is the more capable timing tool if you use a countdown timer, need multiple daily alarms, or want world time and finer stopwatch resolution.
How do the designs differ?
GMA-S160: compact, rounded styling
Casio positions the S160 as a compact, slim design. The cited S160-7A page also identifies bio-based resin in key bezel and band components. Choose it if its softer, rounded look and reduced size suit your taste.
Rank #2
- Magnetic resistant, shock resistant, 200-meter water resistance, led light, world time, stopwatch, countdown timer
- 5 daily alarms, hourly time signal, full auto-calendar, 12/24-hour format, approx. Battery life: 3 years on cr1220
- Quartz Movement
- Case Diameter: 49mm
- Water resistant 200m (660ft): in general, suitable for professional marine activity and serious surface water sports, but not diving
GMA-S2100: octagonal bezel and flatter face
The S2100 follows the distinctive octagonal-bezel look associated with the GA-2100, with a flat face, simple bar hour markers, and Carbon Core Guard construction. Casio describes the design as a compact configuration of those features on its GMA-S2100-4A product page. The cited S2100-1A is the variant used for the dimensions and weight in this comparison.
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What do their shared ratings and battery estimates mean?
Casio lists shock resistance and 200-metre/20-bar water resistance for both cited variants. This rating is not, by itself, evidence of a specific dive certification. Mineral glass and double LED lighting are also listed for both.
Rank #3
- This high-quality watch has a black plastic strap (21 cm length and 20 mm width) with a pin buckle
- Case diameter: 40 mm, case height: 11 mm, case colour: black. Dial colour: black
- Waterproof: 20 bars -Weight: 42 g
- International products have separate terms, are sold from abroad and may differ from local products, including fit, age ratings, and language of product, labeling or instructions.
Casio estimates approximately three years of battery life for each cited variant, but this is not a guaranteed service interval or a controlled comparison of real-world use. The models use different batteries: one CR1025 in the S160-7A and two SR726W cells in the S2100-1A. Actual life depends on use.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Which G-Shock should you choose?
- Choose the GMA-S160 if your leading concern is a smaller, lighter watch, or if dual time and a basic stopwatch are enough for you.
- Choose the GMA-S2100 if you prefer the octagonal bezel and want the listed world-time, countdown, alarm, and more precise stopwatch features.
Prices, stock, and available colors vary by region and date. Before buying, confirm the model suffix and specifications on the official page for the variant being sold: GMA-S160-7A or GMA-S2100-1A.
Quick Recap
Best Value
- Case size (L× W× H): 46 × 40.2 × 11.2 mm
Rank #4
- It is slim, lightweight, and compact in design and boasts a chic, monochromatic look
- Shock Resistant
- Carbon Core Guard structure
- Double LED light: LED light for the face & LED backlight for the digital display
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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