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Choose the F-91W for the lightest, simplest resin-strap watch; choose the A158 for a compact stainless-steel bracelet and vintage appearance; choose the A168 when a fully illuminated display is worth a little more size and weight. Their stopwatch, alarm, calendar, battery estimate and stated accuracy are effectively the same, so the decision is mainly about comfort, bracelet style, dimensions and nighttime visibility.
The short answer
These three Casio digitals share the same basic job: show the time, provide a stopwatch, sound a daily alarm or hourly signal, and keep an automatic calendar. Casio lists the same CR2016 battery estimate of approximately seven years and the same stated accuracy of ±30 seconds per month for each model. You are not choosing between different movement feature sets.
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The meaningful differences are physical. The F-91W-1 weighs 21 g and uses a resin case and resin band. The A158WEA-7 weighs 45 g, keeps a resin case but adds a stainless-steel band. The A168WA-1 weighs 50 g, uses a resin/chrome-plated case with a stainless-steel band, and adds an electro-luminescent backlight that illuminates the whole display. That makes the F-91W the comfort and low-weight choice, the A158 the compact metal-bracelet choice, and the A168 the readability choice.
Specifications at a glance
| Model | Case size | Weight | Band and case | Light | Battery | Core functions |
|---|---|---|---|---|---|---|
| F-91W-1 | 38.2 × 35.2 × 8.5 mm | 21 g | Resin case and resin band | Green LED | CR2016, approximately 7 years | 1/100-second stopwatch, daily alarm, hourly signal, auto-calendar, 12/24-hour format, ±30 sec/month |
| A158WEA-7 | 36.8 × 33.2 × 8.5 mm | 45 g | Resin case and stainless-steel band | Green LED | CR2016, approximately 7 years | 1/100-second stopwatch, daily alarm, hourly signal, auto-calendar, 12/24-hour format, ±30 sec/month |
| A168WA-1 | 38.6 × 36.3 × 9.6 mm | 50 g | Resin/chrome-plated case and stainless-steel band | Blue-green EL backlight | CR2016, approximately 7 years | 1/100-second stopwatch, daily alarm, hourly signal, auto-calendar, 12/24-hour format, ±30 sec/month |
Casio’s official product pages, captured on October 15, 2026, label all three variants “Water Resistant” but do not provide a numeric depth rating. Treat that wording as everyday splash resistance rather than a swimming specification.
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F-91W: the lightest and simplest option
The F-91W-1 is the practical baseline. At 21 g, it is 24 g lighter than the A158 and 29 g lighter than the A168. That difference is large enough to matter if you dislike a bracelet’s weight, notice your watch while typing, or simply want the least noticeable watch possible.
Its resin case and resin band also create a different wearing experience from the two metal-bracelet models. The strap does not give you the visual flash of a steel bracelet, but it keeps the watch visually and physically simple. For a wearer who wants a basic digital timer, alarm and calendar without a metal band, the F-91W meets that brief directly.
The case measures 38.2 × 35.2 × 8.5 mm. It is slightly longer and wider than the A158 despite being much lighter, because the A158’s weight comes primarily from its stainless-steel band. Its green LED is functional but localized rather than a full-screen glow, so the display can be less immediately legible in darkness than the A168’s EL panel.
Casio’s official F-91W page describes the model this way: “Since its debut in 1989, it has captured hearts worldwide and adorns the wrists of celebrities, both in real life and on the big screen.” That is Casio’s own historical and promotional statement; it does not change the practical comparison, but it explains why the F-91W remains the reference point for this group.
A158: the compact metal-bracelet alternative
The A158WEA-7 keeps a resin case but replaces the F-91W’s resin strap with a stainless-steel bracelet. At 36.8 × 33.2 × 8.5 mm, it is 1.4 mm shorter and 2.0 mm narrower than the F-91W, while retaining the same 8.5 mm thickness. It is therefore the smallest case of the three by the published dimensions.
That compact case does not make it the lightest. The A158 weighs 45 g, more than twice the F-91W’s 21 g. If you want the appearance and feel of a metal bracelet, that mass is the trade-off. If you are sensitive to weight, the A158 can feel substantially more present on the wrist even though its case is smaller.
Casio describes the A158’s bracelet as self-adjustable. That gives you a way to size the band to your wrist without changing to a resin strap. The bracelet is the reason to choose this model, not a different stopwatch, alarm or battery system: those specifications match the F-91W.
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- Ideal for Gifting
- Ideal for a bookworm
- Compact for travelling
The A158 uses the same green LED approach as the F-91W. It is suitable for checking the display in low light, but it does not provide the evenly illuminated screen supplied by the A168’s EL panel. For daytime wear and occasional nighttime checks, the A158’s light may be sufficient; for frequent dark-room reading, the A168 has the stronger case.
A168: the backlight specialist
The A168WA-1 is the largest and heaviest model in this comparison. Its case measures 38.6 × 36.3 × 9.6 mm and its total weight is 50 g. Compared with the A158, it is 1.8 mm longer, 3.1 mm wider, 1.1 mm thicker and 5 g heavier. Compared with the F-91W, it is 0.4 mm longer, 1.1 mm wider, 1.1 mm thicker and 29 g heavier.
The reason to accept those numbers is the blue-green electro-luminescent backlight. Casio’s Singapore product information explains that the EL panel is a thin, sheet-like panel that evenly illuminates the display. Instead of relying on a small LED glow, the A168 lights the entire display area, making it the clearest choice when you regularly read the watch at night.
The A168 still uses a stainless-steel bracelet and Casio lists it as self-adjustable. Its case is described as resin/chrome-plated rather than plain resin. That gives it the metal-bracelet appearance associated with the A158 while adding the full-display lighting that the A158 lacks.
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1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsThe A168 is not a feature upgrade in every category. Its stopwatch, alarm, hourly signal, calendar, 12/24-hour format, battery type, approximate battery life and stated accuracy are the same as the other two. You are paying in wrist weight and a slightly larger case for the lighting system and its associated styling, not for additional timing modes.
Weight and comfort: how the 21 g, 45 g and 50 g figures translate
When the F-91W makes the most sense
Choose the F-91W if you often remove watches because they feel distracting. Its 21 g total weight is 24 g below the A158 and 29 g below the A168. That is not a small specification difference: the band, case and clasp together create a noticeably lighter object on the wrist.
The F-91W is also the straightforward option for people who prefer a flexible resin strap over a bracelet. The decision is subjective, but the published weight gives you an objective starting point: among these three, nothing is lighter.
When the A158 is the balanced bracelet choice
The A158 occupies the middle position at 45 g. It is the smallest case, yet it is still more than twice the F-91W’s weight because of its stainless-steel band. This can appeal to someone who wants a compact watch head and a classic digital-metal look without moving to the A168’s thicker case and EL system.
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When the A168’s extra 5 g is justified
The A168 adds only 5 g over the A158, but that extra weight accompanies a larger, 9.6 mm-thick case and the full EL backlight. If night visibility is a daily requirement, those are purposeful additions. If you rarely use the light, the A158 avoids the extra size while preserving the bracelet style.
Resin strap versus stainless-steel bracelet
The band material is the clearest visual and tactile split. The F-91W uses resin for both case and band. The A158 combines a resin case with stainless steel, and the A168 combines a resin/chrome-plated case with stainless steel.
- Resin on the F-91W: the lowest listed weight and the simplest appearance. It is the logical choice when comfort and unobtrusiveness outrank bracelet styling.
- Stainless steel on the A158: a compact case with a metal-bracelet presentation. Its self-adjustable bracelet lets you size it to your wrist.
- Stainless steel on the A168: the bracelet look plus the largest case and EL lighting. The trade-off is the highest listed weight.
None of the published specifications establishes a durability advantage for one band material. There is no independent wear or durability testing attached to these figures, so choose the material for fit, appearance and weight rather than assuming one will last longer.
Night readability: green LED or full-display EL?
How the F-91W and A158 differ from the A168
The F-91W and A158 both use a green LED. Their lighting specification is therefore the same, and neither has the A168’s sheet-like panel covering the display. They can still provide a quick low-light time check, but the illumination is not described as a full-display wash.
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Why the A168 is the night-reading pick
The A168’s blue-green EL backlight is designed to illuminate the entire display evenly. That matters if you check the time in a dark bedroom, a dim commute, a theater or another setting where a partial glow makes digits harder to read. The benefit is visibility, not a new function: the underlying timekeeping and alarm features remain shared with the other models.
If you ask, “Is the A168 worth it for the backlight?”, the answer depends on frequency. For occasional nighttime checks, the A158 or F-91W may be adequate. For repeated or effortless reading in darkness, the A168 is the only model here with the full-display EL system, so it is the defensible upgrade.
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Are the A158 and A168 the same size?
No. They share the stainless-steel-bracelet concept, but their published dimensions are different. The A158 is 36.8 × 33.2 × 8.5 mm; the A168 is 38.6 × 36.3 × 9.6 mm. The A168 is longer, wider and thicker, and weighs 5 g more.
The difference is modest on paper but relevant on a smaller wrist or under a sleeve. The A158 has the more compact case. The A168 has the more substantial presence and adds the EL panel. Treat them as related designs rather than interchangeable sizes.
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Casio lists the following functions for all three variants:
- 1/100-second stopwatch
- Daily alarm
- Hourly signal
- Automatic calendar
- 12- or 24-hour time format
- Stated accuracy of ±30 seconds per month
The shared list changes the buying logic. There is no model in this trio with a longer published battery estimate, a more accurate stated module or an additional timing mode. Select the case, band and light first; then use the common feature set as confirmation that any of the three covers basic digital-watch duties.
The ±30-seconds-per-month figure is Casio’s stated specification, not a guarantee that every individual watch will show exactly the same drift in every environment. It is the number to use when comparing these models, because Casio publishes it for all three.
Battery life and maintenance
Each watch uses a CR2016 cell, and Casio gives an approximate seven-year battery life for each model. Battery life therefore does not separate the F-91W, A158 and A168 on the published figures.
“Approximately” matters: the estimate is not a promise of an identical replacement date for every watch. Alarm use, light use and storage conditions can affect real-world service intervals, but the available specifications do not quantify those effects. When a cell eventually needs replacing, use the specified CR2016 type and have the work done carefully so the case and water-resistance condition are not compromised.
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The A168’s EL lighting should not be treated as evidence of a shorter published battery life; Casio still lists approximately seven years for it, the same as the LED-equipped models. If battery longevity is your deciding criterion, the official numbers produce a tie.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Water resistance: can you swim with one?
Casio labels the F-91W-1, A158WEA-7 and A168WA-1 “Water Resistant.” The official pages supplied for these variants do not state a numeric depth rating. Without that rating, there is no evidence here to classify any of them for swimming, snorkeling or intentional submersion.
Use the label conservatively for everyday splash exposure, such as incidental rain or hand-washing situations, and avoid promising yourself swimming suitability. If swimming capability is essential, choose a watch whose official specifications explicitly provide an appropriate water-resistance depth rating; none is provided for these three variants in the cited specifications.
Which model should you buy?
Choose the F-91W-1 if comfort is the priority
- You want the lowest possible listed weight: 21 g.
- You prefer a resin band and do not need a stainless-steel appearance.
- You use the stopwatch, alarm and calendar but only need a basic green LED at night.
- You want the least noticeable option for all-day wear.
Choose the A158WEA-7 if the bracelet look matters most
- You specifically want a stainless-steel bracelet with a compact case.
- You prefer the smallest published case dimensions: 36.8 × 33.2 × 8.5 mm.
- You can accept 45 g instead of the F-91W’s 21 g.
- A green LED is sufficient for your low-light checks.
Choose the A168WA-1 if you read the watch in darkness
- You want an evenly illuminated display from the blue-green EL panel.
- You prefer a stainless-steel bracelet but do not mind the largest case.
- The 50 g weight and 9.6 mm thickness are acceptable in exchange for readability.
- You want the A158-style bracelet concept with a stronger nighttime-lighting solution.
A practical decision sequence
- Decide whether you want resin or metal on your wrist. Resin points to the F-91W; stainless steel points to the A158 or A168.
- Set your weight limit. At 21 g, the F-91W is the only very-light option. The A158 is 45 g and the A168 is 50 g.
- Decide how important darkness readability is. Occasional checks favor either green-LED model; frequent dark reading favors the A168’s EL panel.
- Check case dimensions against your wrist and sleeves. The A158 is smallest; the A168 is largest and thickest; the F-91W sits between them in length and width but remains the lightest.
- Ignore battery life as a tie-breaker. All three use CR2016 cells with Casio’s approximate seven-year estimate.
- Keep water use conservative. “Water Resistant” is not a published swimming rating for these variants.
Common buying mistakes
Assuming the A158 is lighter because its case is smaller
The A158 has the smallest case, but its stainless-steel bracelet brings the total to 45 g. The F-91W’s larger-looking dimensions do not make it heavier; its resin construction keeps it at 21 g.
Paying for the A168 without needing its light
The A168’s distinguishing feature is the EL backlight. If you mostly read your watch in daylight, you may be carrying a 50 g, 9.6 mm-thick watch without using the feature that sets it apart from the A158.
Expecting different stopwatch or alarm capabilities
Casio lists the same core functions for all three. The A158 and A168 are not functionally advanced stopwatch models compared with the F-91W; their differences are physical and optical.
Interpreting “Water Resistant” as a dive or swim rating
No numeric depth rating is supplied for these variants. Treating the label as permission for swimming goes beyond the published evidence.
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| Your priority | Best match | Reason |
|---|---|---|
| Minimum weight and resin comfort | F-91W-1 | 21 g, resin case and resin band |
| Compact stainless-steel bracelet | A158WEA-7 | Smallest case at 36.8 × 33.2 × 8.5 mm and a self-adjustable steel band |
| Full-display nighttime visibility | A168WA-1 | Blue-green EL panel that evenly illuminates the display |
| Longest published battery estimate | All three tie | CR2016 and approximately seven years for each |
| Swimming suitability | No confirmed choice from these specifications | All are labeled Water Resistant without a numeric depth rating |
For most buyers, the final choice is simple: F-91W for lightness, A158 for the smallest metal-bracelet package, and A168 for the best darkness readability. The shared functions and battery figures mean you should spend your attention on the way each one sits, weighs and lights on your wrist.
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