The Casio F105W vs F91W comparison is one of the easiest ways to understand how small details can change a cheap digital watch. On paper, these two watches look very similar. Both are lightweight, affordable, simple, water resistant, battery-powered Casio digital watches with a stopwatch, alarm, calendar and resin case.
But they are not exactly the same watch.
The Casio F91W is the more iconic model. It is thinner, more famous, more recognizable and has the classic old-school Casio look. The Casio F105W is very close in size and function, but it adds one major upgrade: a much better Illuminator-style backlight.
That single difference matters a lot. If you often check the time in the dark, the F105W is the more practical watch. If you want the most iconic cheap Casio, the F91W is still the one to buy.
Quick Verdict
| Buyer type | Better choice | Why |
|---|---|---|
| Best classic Casio | Casio F91W | More iconic and historically important |
| Best backlight | Casio F105W | Much easier to read in the dark |
| Best slim feel | Casio F91W | Thinner case |
| Best for night use | Casio F105W | Better illumination |
| Best for collectors | Casio F91W | More recognizable and more culturally important |
| Best practical daily choice | Casio F105W | Same basic idea, better light |
| Best minimalist digital watch | Casio F91W | Cleaner and slimmer |
| Best for small wrists | Both | Both are very light and compact |
| Best if you already own an F91W | Casio F105W | Worth adding only if you want better backlight |
| Best overall for most users | Casio F105W | The backlight upgrade is genuinely useful |
Short answer: buy the F91W if you want the icon. Buy the F105W if you want the better cheap Casio for reading the time at night.
Casio F105W vs F91W: Main Differences
| Feature | Casio F91W | Casio F105W |
|---|---|---|
| Watch type | Classic digital Casio | Classic digital Casio with better light |
| Case size | 38.2 × 35.2 × 8.5 mm | 39 × 35.4 × 9.6 mm |
| Weight | 21 g | 21 g |
| Case / bezel material | Resin | Resin |
| Band | Resin band | Resin band |
| Glass | Resin glass | Resin glass |
| Water resistance | Water Resistant | Water Resistant |
| Battery | CR2016 | CR2016 |
| Approx. battery life | About 7 years | About 7 years |
| Stopwatch | 1/100-second stopwatch | 1/100-second stopwatch |
| Alarm | Daily alarm | Daily alarm |
| Backlight | Basic small light | Better Illuminator / EL-style backlight |
| Best for | Iconic cheap digital watch | Cheap digital watch with better night visibility |
The F105W is not a completely different watch. It is more like an F91W-style watch with a better light and a slightly thicker case.
Design and Wrist Feel
The F91W is the cleaner and more iconic design. It has the familiar black case, blue outline, red “WR” mark and classic rectangular display. It looks exactly like what many people imagine when they think of a cheap Casio digital watch.
The F105W keeps the same basic formula but looks a little more modern and slightly bulkier because of the Illuminator design. It is still small, light and easy to wear, but it does not feel quite as thin as the F91W.
| Wearing factor | Casio F91W | Casio F105W |
|---|---|---|
| Thickness | Thinner | Slightly thicker |
| Weight | 21 g | 21 g |
| Wrist presence | Very small and discreet | Still small, but a bit more noticeable |
| Sleeve comfort | Excellent | Excellent, but not quite as thin |
| Retro look | Stronger | Slightly more modern |
| Iconic style | Better | Good, but less famous |
Comfort
Both watches are extremely comfortable. At 21 g, they almost disappear on the wrist. If you dislike heavy watches, both are excellent.
The F91W has the advantage if you want the thinnest possible feel. The F105W has the advantage if you do not mind a tiny bit of extra thickness in exchange for a better backlight.
Backlight: The Biggest Difference
This is the real reason to choose the Casio F105W over the F91W.
The F91W backlight is famous, but not always for good reasons. It is a small side light that illuminates the display unevenly. It works, but it is weak. You can read the time in the dark, but it does not feel modern or especially comfortable.
The F105W has a much better Illuminator / EL-style backlight. It lights the display more evenly and makes the watch far easier to read at night.
| Backlight factor | Casio F91W | Casio F105W |
|---|---|---|
| Brightness | Weak | Much better |
| Display coverage | Uneven | More even |
| Night readability | Acceptable | Clearly better |
| Best for dark rooms | Not ideal | Better |
| Best for checking time in bed | Weak but usable | Much better |
| Main reason to buy | Iconic design | Backlight upgrade |
This is not a small upgrade. If you use the light often, the F105W is objectively more useful.
My honest opinion
The F91W is cooler. The F105W is more practical. The F91W wins emotionally; the F105W wins at night.
Functions and Everyday Use
Functionally, the F91W and F105W are very close. Both give you the basic Casio digital package: time, calendar, alarm, hourly signal, stopwatch and light.
Neither is a smartwatch. Neither has sensors. Neither has Bluetooth. Neither is a rugged G-Shock. These are simple cheap digital watches.
| Function | Casio F91W | Casio F105W |
|---|---|---|
| Time | Yes | Yes |
| Calendar | Yes | Yes |
| 12/24-hour format | Yes | Yes |
| Daily alarm | Yes | Yes |
| Hourly time signal | Yes | Yes |
| 1/100-second stopwatch | Yes | Yes |
| Backlight | Yes, basic | Yes, better |
| Water resistance | Basic | Basic |
| Long battery life | Yes | Yes |
For normal daily use, both are enough. The difference appears when you use the backlight.
Water Resistance
Both watches are listed as Water Resistant. That means they can handle normal daily moisture, but they are not watches I would buy specifically for swimming.
In practical use, they are usually fine for rain, sweat, splashes and hand washing. But if you want regular swimming, beach use or stronger water confidence, buy a G-Shock or a more water-focused Casio.
Neither watch wins here in a meaningful way. If water resistance matters, neither is the best choice.
Battery Life and Maintenance
Both watches use a CR2016 battery and are officially rated for around 7 years of battery life. That is excellent for such cheap watches.
| Battery factor | Casio F91W | Casio F105W |
|---|---|---|
| Battery type | CR2016 | CR2016 |
| Approx. battery life | About 7 years | About 7 years |
| Replacement cost | Cheap | Cheap |
| Solar power | No | No |
| Charging needed | No | No |
| Maintenance | Very low | Very low |
The F105W has a better backlight, but Casio still lists the same approximate battery life. In real life, using the light constantly will always affect battery life, but for normal use both are low-maintenance watches.
Durability and Build Quality
The F91W and F105W are reliable for the money, but neither should be confused with a G-Shock.
They are basic resin digital watches. They can handle everyday wear, but they are not built for serious impact, rough work or heavy water use.
| Durability factor | Casio F91W | Casio F105W |
|---|---|---|
| Daily wear | Good | Good |
| Light sport | Good | Good |
| Drops and bumps | Basic protection | Basic protection |
| Serious impact | Not ideal | Not ideal |
| Resin glass scratches | Possible | Possible |
| Strap durability | Basic | Basic |
| Long-term toughness | Good for price | Good for price |
If you need real durability, do not overthink F91W vs F105W. Buy a G-Shock DW-5600 or GW-M5610.
Price and Value
Usually, both watches are affordable. The F91W is often cheaper and easier to find. The F105W may cost a little more depending on the market, but the better light can justify the difference.
| Value question | Better choice |
|---|---|
| Cheapest option | F91W |
| Best practical upgrade | F105W |
| Best if prices are close | F105W |
| Best collector icon | F91W |
| Best first cheap Casio | F91W |
| Best cheap Casio for night use | F105W |
If the F105W costs only slightly more, it is probably the better functional buy. If the F91W is much cheaper, it remains the better budget choice.
Which One Should You Buy?
Buy the Casio F91W if:
| Reason | Explanation |
|---|---|
| You want the most iconic cheap Casio | The F91W is the legend |
| You prefer a thinner case | It is slimmer than the F105W |
| You like the classic blue/red design | The styling is more recognizable |
| You want the cheapest option | It is often less expensive |
| You do not use the backlight much | Then the F105W upgrade matters less |
| You want a minimalist everyday watch | The F91W does that perfectly |
Buy the Casio F105W if:
| Reason | Explanation |
|---|---|
| You want a better backlight | This is the main advantage |
| You often check the time at night | The display is much easier to read |
| You want F91W-style simplicity with a practical upgrade | That is exactly what it offers |
| You do not mind a slightly thicker case | The difference is small |
| Prices are close | The F105W becomes the smarter buy |
| You already own an F91W | It gives you a useful variation |
My recommendation
For most practical users, I would choose the F105W. The better light is useful every time you check the watch in the dark.
But if you want the true classic, the F91W is still the better emotional choice. It is the one with the stronger identity.
Pros and Cons
| Watch | Pros | Cons |
|---|---|---|
| Casio F91W | Iconic, very cheap, thin, light, simple, long battery life | Weak backlight, basic water resistance, basic resin glass |
| Casio F105W | Much better backlight, still cheap, light, simple, long battery life | Slightly thicker, less iconic, less classic design |
| Both | Affordable, reliable, comfortable, easy to wear, simple digital functions | Not G-Shocks, not swim watches, no advanced features |
Final Verdict
The Casio F105W and F91W are both excellent cheap digital watches, but they are good for slightly different reasons.
The F91W is the icon. It is thinner, more recognizable and more historically important. If you want the classic cheap Casio, buy the F91W.
The F105W is the more practical watch. It keeps the same lightweight digital idea but adds a much better backlight. If you actually use your watch at night, the F105W is easier to live with.
So the final answer is simple:
F91W for the classic.
F105W for the better light.
If you care about history and style, choose the F91W. If you care about usability, choose the F105W.
FAQ
What is the difference between Casio F105W and F91W?
The biggest difference is the backlight. The F105W has a much better Illuminator / EL-style backlight, while the F91W has a weaker side light.
Is F105W better than F91W?
The F105W is better for night readability. The F91W is better if you want the more iconic and thinner watch.
Is the Casio F105W bigger than the F91W?
Yes, slightly. The F105W is 39 × 35.4 × 9.6 mm, while the F91W is 38.2 × 35.2 × 8.5 mm.
Do F105W and F91W have the same battery?
Yes. Both use a CR2016 battery and are rated for about 7 years of battery life.
Are F105W and F91W waterproof?
No. Both are water resistant, not true waterproof watches. They are fine for daily splashes, but not ideal for swimming.
Which has a better backlight, F105W or F91W?
The F105W has a much better backlight.
Which is more comfortable, F105W or F91W?
Both are very comfortable and weigh 21 g. The F91W is slightly thinner, so it feels a little more minimal.
Is the F105W a G-Shock?
No. The F105W is a basic Casio digital watch, not a G-Shock.
Which is better for everyday use, F105W or F91W?
For most people, the F105W is more practical because of the better backlight. The F91W is better if you value the iconic design.
Should I buy Casio F105W or F91W?
Buy the F91W if you want the classic. Buy the F105W if you want the better light.
