Index / SR60 / SR60 vs SR66

SR60 vs SR66: what differs, and which goes where

SR60 and SR66 share the same 6.8 mm diameter, 2.2 mm against 2.6 mm deep. SR60 is a silver oxide cell at 1.55 V; SR66 is a silver oxide cell at 1.55 V. SR66 in a holder built for SR60: too tall, at 1.55 V against 1.55 V. SR60 in a holder built for SR66: sits lower, at 1.55 V against 1.55 V.

Warning — button cell

SR60 is a button cell: 6.8 mm across and 2.2 mm tall. If one has been swallowed, or put in a nose or an ear, call the United States national Poison Help line at 1-800-222-1222 straight away and do not wait for symptoms.

Why this shape is dangerous, and the law behind the pack

United States law defines that class by the shape alone — a single cell battery with a diameter greater than its height, 16 CFR 1263.2 — and not by what is inside it. Swallowed, a cell this shape can lodge instead of passing, and it is the current, not the metal, that does the damage.

At 6.8 mm and 1.55 V it is under the 16 mm diameter that lodges most readily — which makes it easier to swallow, not safer. The same current runs for as long as it sits.
Reese's Law (15 U.S.C. 2056e) and 16 CFR part 1263 put child-resistant packaging and a warning label on this class; packages manufactured or imported after 21 September 2024 carry it. That is why the pack is hard to open.
The same rule says what to do with the used cell, in its own words: dispose of it at once, keep it away from children, and do NOT put it in household trash (16 CFR 1263.4(b)(3)). Tape over both faces first — a cell too flat to run a watch still has enough left to burn.

Side by side

Every figure below is published by the maker for SR60 and SR66; the last column is ours, the difference read off the printed tenths of a millimeter.

SR60 and SR66, published figures
Figure	SR60	SR66	Difference
Diameter	6.8 mm	6.8 mm	same
Height	2.2 mm	2.6 mm	+0.4 mm
Nominal voltage	1.55 V	1.55 V	same
Chemistry	silver oxide	silver oxide	same
Capacity	19 mAh	24 mAh	—
Stored energy	29 mWh	37 mWh	—
In the Energizer catalog	listed	listed	—
Sold as	SR60, 364, SG1, SR621SW, 1175SO	SR66, 377, SG4, SR626SW, SR626W, 376, 1176SO	—

Either way round

Fit and voltage are separate answers, and they change with direction: the holder is built for one cell, and the other has to live with it. SR60 is 2.2 mm deep and SR66 is 2.6 mm.

SR66 in a holder built for SR60 — SR66 stands 0.4 mm taller and stops the cover closing; it runs 1.55 V against the 1.55 V the device expects, the same working voltage.
SR60 in a holder built for SR66 — SR60 goes in and stands 0.4 mm lower, a gap a spring contact usually takes up; it runs 1.55 V against the 1.55 V the device expects, the same working voltage.

From BatteryCrossEvery designation in one pageEach code with what it measures and what it replaces

Drawn to scale

Both at one scale. The dashed line marks the height of SR66: SR60 stops 0.4 mm short of it.

This cellAnother cell, same scale

How long each one runs

SR60 holds 19 mAh at 1.55 V, about 29 milliwatt-hours; SR66 holds 24 mAh, about 37. In the same device SR66 runs noticeably longer, 1.3 times, which is the whole reason the bigger cell exists. Price follows less closely than energy does. Per cubic centimeter SR60 packs 368 milliwatt-hours against 413 for SR66, so the difference is construction, not only size.

What each one is made for

Both are made for watches, calculators and small instruments that draw very little, which is why they end up in the same drawer and get mixed up: SR60 at 1.55 V and SR66 at 1.55 V. Read the code off the old cell before buying: the device was designed around that one, and the drawing above is how the other one sits in it.

Silver oxide (SR60, 1.55 V) holds its voltage almost flat until it is spent, which is why watches and light meters were built around it.

What the codes and the sheets add

SR60 does not encode its size, so only the sheet says it; SR66 does not encode its size, so only the sheet says it. Beyond size and voltage, the sheets say this: SR60 weighs 0.3 g and SR66 weighs 0.4 g.

Telling them apart in the hand

The code is printed on the flat face of each: SR60 on one, SR66 on the other. Stood side by side, SR66 is 0.4 mm deeper, about 1.18 times the height of SR60, which a caliper reads at once and a ruler barely shows. If the old cell is gone and the code with it, measure the holder instead: its depth and its opening are what this page compares.

Names on the package

SR60 also appears as 1175SO, 364 and 364/363 in Energizer's own part numbers, and other brands sell it as 364, SG1 and SR621SW; SR66 also appears as 376, 1176SO and 377 in Energizer's own part numbers, and other brands sell it as 377, SG4 and SR626SW. Energizer lists both, which says what is on the shelf under these numbers and nothing about who else still makes them.

Which one to buy

Buy the code printed on the old cell or named in the manual. In a pinch SR60 can stand in where SR66 sat, at 1.55 V against 1.55 V. Both pages carry the full figures and sources: SR60 and SR66.

Before you swap anything

Everything here is computed from published dimensions and nominal voltages. That answers whether a cell enters the compartment and whether the voltage matches on paper. It does not answer what your device does with the difference, and it cannot: a cell that fits can still be the wrong cell.

One more limit, and it is the biggest. This site reads a single manufacturer’s catalog. When a page says a designation is not listed, that means Energizer no longer offers a part under it — not that nobody makes the cell. Other makers may still sell it, and for common sizes they usually do.

A voltage difference is one relation between two cells, and this page prints it from the cell it is about — in every table on the page, including the one listing cells no longer made. A figure always belongs to the cell whose voltage is printed beside it: a cell that runs lower than this one carries a minus here, one that runs higher carries a plus, and two cells at the same nominal voltage carry zero. Meet the same pair on the other cell’s page and the sign is the other one, with the figure taken against that cell instead of this one; where the two run at the same voltage, both pages print zero. The class beside the figure is not read off that figure directly. It is decided on the gap itself, taken against the higher of the two nominal voltages, so one pair of cells gets one class whichever page you meet it on: counted from this side the boundary of the class that still runs falls at 20.0% below and 25.0% above, which is the same gap divided once by the larger nominal and once by the smaller. What genuinely differs between the two directions is the consequence, and the words carry it: a cell that runs low makes a calibrated instrument read below true, and a cell that runs high makes it read above.

3 things this site cannot see. Whether the contacts reach a shorter cell. Whether the device was calibrated for a chemistry that holds its voltage flat, which silver oxide does and alkaline does not. Whether the equipment tolerates the higher current a different chemistry can deliver. Rechargeable cells are never a drop-in for primary cells regardless of size.

Where these numbers come from

Dimensions, voltages, chemistries and capacities are published by the manufacturer and reproduced without change. Everything else on the page is ours, computed from those figures: whether one cell fits where another sat, how far apart their voltages are, stored energy and energy per cubic centimeter, the rank within a shell, and the check of the designation against the measured size.

Fit is decided within 0.3 mm on every axis, which is the order of a contact spring's travel. Voltage classes are decided by consequence, not by roundness, and they are decided on the gap between two nominal voltages taken against the higher of the two: 2.0% or less of it is the same working voltage, 6.0% starts to matter to a calibrated instrument, and past 20.0% it is a different class altogether. Measuring the gap against the higher figure is what makes the verdict the same from either cell’s page, while the printed percentage stays counted from the cell you are reading about. Cells with identical stored energy share a rank instead of being ordered arbitrarily.

Ranking uses capacity times nominal voltage, because capacity alone is not comparable across chemistries: 150 mAh at 3 V is twice the energy of 150 mAh at 1.5 V. Neighbors are chosen by measurement and never alphabetically, because two cells filed next to each other by name usually have nothing in common. A blank in any table means the maker publishes no figure, which is not the same as zero.

Source: Energizer technical data, retrieved 1 September 2026.