Quick Verdict
The GA-2100 solved the problem that kept G-Shock off most wrists: thickness. At 11.8 mm and 51 g it fits under a cuff, and it keeps the shock resistance and 200 m rating that made the line matter in the first place.
At a Glance
- Street price
- $99
- Movement type
- Quartz
- Power reserve
- Battery, approximately 3 years
- Case diameter
- 45.4 mm
- Lug-to-lug
- 48 mm
- Crystal
- Mineral
- Water resistance
- 200 m (656 ft)
Design
An octagonal bezel over a thin resin case, with analog hands and a small digital window at the bottom of the dial. It is the most restrained G-Shock design in the catalogue, which is why it reached an audience the line had never had.
Movement
Casio module 5611: analog hands driven alongside a digital display, with world time, stopwatch, countdown timer and alarms. Casio specifies ±15 seconds per month and roughly three years of battery life.
Build Quality
Carbon Core Guard construction places the module inside a carbon-fibre-reinforced resin case. It carries the full G-Shock shock-resistance specification and a 200 m water rating.
Dial
Applied resin indices with luminous fill and a small LCD panel. Legibility is good in daylight and depends on the backlight at night — the digital window is the weakest element of the layout.
Bracelet & Strap
The resin strap is integrated into the case. Adapters exist for conventional straps, but the watch is designed around the strap it ships with.
Comfort & Wearability
51 g and 11.8 mm makes this the lightest watch in this database. It fits essentially any wrist, which is unusual for a case measuring 45.4 mm at its widest.
Accuracy
Casio publishes ±15 seconds per month. Unlike the solar Citizen models it requires a battery change roughly every three years.
What we like
What we like
- 11.8 mm — by far the slimmest G-Shock case
- Carbon Core Guard construction with 200 m water resistance
- 51 g, light enough to sleep in
- Analog hands plus a digital display without visual clutter
What we don't like
- Mineral crystal that scratches more easily than sapphire
- The digital display is small and low contrast
- Integrated strap cannot be swapped without an adapter
Who Should Buy It?
Anyone who wants a genuinely indestructible watch that still fits under a shirt, and anyone looking for a first watch that will survive anything.
Who Should Skip It?
Skip it if you want a mechanical movement or a watch that reads as formal. Skip it if the small digital display bothers you — the GW-M5610U is the better pure digital.
Best Alternatives
Three watches worth weighing up before you commit.
How It Compares
G-Shock GA-2100
3 categories won
G-Shock GW-M5610U
2 categories won
- Street price
- $99Winner
- $130
- Movement type
- Quartz
- Solar
- Caliber
- 5611
- 3495
- Power reserve
- Battery, approximately 3 years
- Approximately 10 months from a full charge
- Stated accuracy
- ±15 seconds per month (Casio specification)
- ±15 seconds per month without radio sync (Casio specification)
- Case diameter
- 45.4 mm
- 46.7 mm
- Case thickness
- 11.8 mmWinner
- 12.7 mm
- Lug-to-lug
- 48 mm
- 46.7 mmWinner
- Crystal
- MineralEven
- MineralEven
- Water resistance
- 200 m (656 ft)Even
- 200 m (656 ft)Even
- Bracelet / strap
- Integrated resin strap
- Integrated resin strap
- Weight
- 51 gWinner
- 53 g
- Style
- Sport · Everyday · Digital
- Digital · Sport · Everyday
- Recommended wrist
- Small · Medium · Large
- Small · Medium · Large
- Selection Score
- 88 / 100
- 91 / 100Winner
Final Verdict
The most wearable G-Shock ever made and one of the best-value watches at any price. The mineral crystal is the only specification worth complaining about.
Specifications
- Brand
- G-Shock
- Model
- GA-2100
- Reference
- GA-2100-1A1
- Collection
- Analog-Digital
- Street price
- $99
- MSRP
- $99
- Movement type
- Quartz
- Movement
- Casio module 5611
- Caliber
- 5611
- Power reserve
- Battery, approximately 3 years
- Stated accuracy
- ±15 seconds per month (Casio specification)
- Balance spring
- Not published
- Case diameter
- 45.4 mm
- Case thickness
- 11.8 mm
- Lug-to-lug
- 48 mm
- Lug width
- Integrated
- Weight
- 51 g
- Case material
- Carbon Core Guard resin
- Crystal
- Mineral
- Water resistance
- 200 m (656 ft)
- Dial colours
- Black
- Bracelet / strap
- Integrated resin strap
- Bracelet material
- Resin
- Clasp
- Pin buckle
- Date
- No
- GMT
- No
- Chronograph
- Yes
- Style
- Sport · Everyday · Digital
- Recommended wrist
- Small · Medium · Large
- Country of origin
- Japan
- Released
- 2019
- Selection Score
- 88 / 100
Score Breakdown
- 25%24.0
Value
- 20%14.0
Movement
- 15%13.8
Build Quality
- 15%13.5
Design
- 10%9.4
Wearability
- 10%8.5
Features
- 5%4.5
Brand & Ownership
Seven pillars, each rated 0–10 and weighted as shown. The total is the sum of the weighted ratings — the headline number can never disagree with its own breakdown.
Ratings are demo data pending editorial review.
Where to Buy
Selection Time is reader-supported. If you buy through a link on this page we may earn a commission. This never affects our scores or what we recommend.
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Amazon
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G-Shock US
$99 · Price checked August 1, 2026
Frequently Asked Questions
Why is the GA-2100 called the CasiOak?
The octagonal bezel invited comparison with the Audemars Piguet Royal Oak, and the nickname spread through collector forums.
Does it have solar charging?
The standard GA-2100 does not. Casio sells GA-B2100 references that add Tough Solar and Bluetooth time sync at a higher price.
