KnowYourBatteries
KnowYourBatteries
Find by thingFind by batteryCan I swap?Measure itGuidesAbout usContact usSwallowed a battery?
Privacy policyTerms of useAffiliate disclosureCookie settings
EnglishEspañolFrançaisDeutsch

As an Amazon Associate, KnowYourBatteries.com earns from qualifying purchases. Battery facts come from the makers’ datasheets.

HomeFind by thingFind by batteryCan I swap?Measure it
Home › Batteries › LR521
Button battery

LR521 battery

1What it is2Safety3Other names4Tip5Facts6Buy it
  1. 1

    What it is

    LR521+ 1.5V

    LR521 is a button battery, about as wide as a pencil eraser. It gives 1.5 volts.

    Search Amazon for LR521As an Amazon Associate, KnowYourBatteries.com earns from qualifying purchases.

    Something wrong or missing? Tell us

  2. 2

    Safety first

    Keep away from children and pets

    A swallowed coin or button battery can cause serious burns inside the body within 2 hours. If you think one was swallowed, get emergency help right away.

    Swallowed one? What to do now →
  3. 3

    Names you might see in the store

    All of these are the same battery. Any of them will work.

    AG0LR63
  4. 4

    A tip before you buy

    SR521SW is the same size and lasts longer

    It costs a little more but gives steadier power. Worth it for cameras, measuring tools and watches. For toys and laser pointers, LR521 is fine.

    About SR521SWCompare the two
  5. 5

    Quick facts

    Size
    About as wide as a pencil eraser
    Thickness
    As thick as 3 credit cards stacked
    Power
    1.5 volts
    Keeps in a drawer for
    About 5 years
    Rechargeable?
    No, use once
    Found in things like
    Small ladies’ watchesCalculatorsSmall remotes
  6. 6

    Where to buy it

    As an Amazon Associate, KnowYourBatteries.com earns from qualifying purchases.

    Amazon searchEnergizer listings, any pack sizeSearch Amazon for Energizer LR521
    See results on Amazon →
    Amazon searchMulti-packs from any brandSearch Amazon for LR521 multi-packs
    See results on Amazon →
    Amazon searchDuracell listings, the same batterySearch Amazon for Duracell LR521
    See results on Amazon →

    Buttons open amazon.com 🇺🇸, picked from your country.

Show more details (optional)

See it at real size

LR521 next to a US quarter and an AA battery. “Real size” matches your hand once your screen is set up in Measure it.

LR521Thickness 2.1US quarterAA

What do the letters mean?

Battery names are a code. Here’s how to read LR521:

LAlkaline chemistry (1.5V)
RRound coin / button form factor
5≈ 5 mm diameter (exact 5.8 mm, 0.228 in)
212.1 mm thickness (exact 2.1 mm, 0.083 in)

The same battery from each brand

BrandTheir name for it
Official nameLR521

Exact measurements

Width
5.8 mm (0.228 in)
Thickness
2.1 mm
Voltage
1.5V (empty at 0.9V)
Energy stored
10 mAh
Weight
—
Made with
Alkaline
Works between
-10 … 60 °C
Official code
LR521

Questions people ask

Is LR521 the same as AG0?

Yes. They’re the same battery with different names. You might also see AG0, LR63.

Can I use SR521SW instead?

Yes, and it’s even better. Same size, but it lasts longer and gives steadier power.

How long will a spare keep in a drawer?

About 5 years if it stays cool and dry.

Can I recharge it?

No. Never try to recharge it.

Which way up does it go?

Usually with the side marked “+” facing you or facing up. Look at how the old one sits before you take it out.

LR521+ 1.5V
LR521Button battery
Search Amazon for LR521As an Amazon Associate, KnowYourBatteries.com earns from qualifying purchases.

Something wrong or missing? Tell us

1What it is2Safety3Other names4Tip5Facts6Buy it