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Casio F-91W
#21 — Best Ultralight Budget Watch

Casio F-91W Review (2026)

0.7 ounces, twenty dollars, and a battery that lasts seven years

★★★★★
8.4/10
Reviewed by William • Updated August 2026 $20

The F-91W has been in production since 1989 and is one of the most-produced watches in history for good reason. It weighs 0.7oz, costs $20, and runs seven years on a battery you can replace anywhere. It has an alarm, a stopwatch, and a backlight. That covers what most hikers use a watch for, at a weight and price where losing it on trail is a shrug rather than a problem. It is not water resistant beyond splashes, and the backlight is genuinely poor.

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$20 retail
TrailCraft Score

What Works

  • 0.7oz — the lightest watch here by a wide margin
  • $20 — replaceable without pain
  • Seven-year battery life
  • Alarm and stopwatch cover most hiking needs
  • Universally available

Limitations

  • Splash resistant only — not for swimming or heavy rain immersion
  • Backlight is dim and short
  • Resin strap breaks eventually
  • No sensors or durability claims

At a Glance

TypeBasic digital
SensorsNone
Battery~7 years, CR2016
Water resistanceSplash only
Weight0.7oz / 20g
FunctionsAlarm, stopwatch, backlight
WarrantyCasio limited

Score Breakdown

Value for Money
9.9
Battery Life
9.6
Durability
7.0
Navigation
2.0
Readability
7.6

What Sets It Apart

Thru-hikers keep arriving at this watch after trying expensive ones. On a five-month trail the things that matter are weight, not needing a charger, and not caring if it breaks. The F-91W wins all three, and the features it lacks turn out not to be missed once the phone handles navigation.

0.7 ounces, twenty dollars, and a battery that lasts seven years

Who This Is For

Thru-hikers, ultralight backpackers, anyone who has broken expensive watches, and hikers who want an alarm and nothing else.

Note: Prices are current as of August 2026. Some links are affiliate links.

Also Consider

See the full comparison

All 30 options in this category ranked side by side.

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Common Questions

Can I get it wet?
Splashes and rain are fine; swimming and sustained immersion are not. The seals are minimal.
Is it worth upgrading from this?
Only if you specifically want sensors, GPS, or real water resistance. For timekeeping alone, no watch here does the job better per gram or per dollar.