Index / SR42
SR42 battery equivalent (344): what to use instead
SR42 silver oxide battery — 1.55 V, 11.6 x 3.6 mm. SR42 and 344 silver oxide batteries of any brand are this same cell. The only other cells this size are ones Energizer no longer lists: MR42. Battery equivalent chart for every other code.
What fits the compartment, and what does not
SR42 battery equivalent chart: candidates for an SR42 battery replacement, one row each. Fit answers whether it enters the compartment. Voltage answers whether the circuit will notice. A cell that fits is not always a safe substitute.
| Cell | Fit | Voltage | Chemistry | Capacity |
|---|---|---|---|---|
| SR54 | sits lower | 1.55 V 0%same volts | silver oxide | 84–90 mAh |
| SR55 | sits lower | 1.55 V 0%same volts | silver oxide | 47–60 mAh |
| LR54 | sits lower | 1.5 V -3.2%close enough | alkaline | 66–80 mAh |
| SR44 | too tall | 1.55 V 0%same volts | silver oxide | 138–200 mAh |
| SR43 | too tall | 1.55 V 0%same volts | silver oxide | 110–127 mAh |
| LR44 | too tall | 1.5 V -3.2%close enough | alkaline | 150 mAh |
| LR43 | too tall | 1.5 V -3.2%close enough | alkaline | 113–123 mAh |
| PR44 | too tall | 1.45 V -6.5%reads off | zinc air | — |
| CR11108 | too tall | 3 V +93.5%wrong class | lithium | 160 mAh |
Nothing Energizer still lists is the same depth. The 9 options below share the diameter and run 2 to 10.8 mm against this cell's 3.6, and some are shallower and some deeper, so read the depth column: short of this cell is a contact problem, past it is a cover problem.
Also stamped 344, 344/350, 350, 387S
The same cell under its full IEC form
The standard writes this designation two ways. SR42 is the short form and SR1136 is the same cell written out; a package may carry either, and 4 of the maker's own part numbers sit beside them.
- SR1136 — the same designation written out in full: the standard's long form for SR42.
- 344 — a manufacturer part number for SR42, not a standard designation; 344 batteries are this same cell, so a 344 battery equivalent is whatever replaces SR42.
- 344/350 — a manufacturer part number for SR42, not a standard designation.
- 350 — a manufacturer part number for SR42, not a standard designation.
- The maker's own catalog carries 4 product lines under it.
The cell that differs only in depth
The code says the size, so the cells that get confused with SR42 are the ones that keep its diameter and change its depth. 17 cells share this diameter at depths from 1.6 to 10.8 mm, and every one of them enters the same opening.
It stands 1 of 2 in this envelope by stored energy. On a scale the difference shows before it shows on a caliper: this one weighs 1.6 g.
- 1177SO — same diameter, 1.6 mm tall against this cell's 3.6: 2 mm shallower, which neither designation carries.
- 365 — same diameter, 1.6 mm tall against this cell's 3.6: 2 mm shallower, which neither designation carries.
- SR55 — same diameter, 2 mm tall against this cell's 3.6: 1.6 mm shallower, which neither designation carries.
- MR42 — the same 11.6 x 3.6 mm in mercuric oxide at 1.4 V. Identical on a caliper, different in the circuit.
- BR1225 — 12.5 mm across at 3 V against 11.6 mm here, 0.9 mm apart: too wide to enter in this holder.
The Energizer data sheets behind this page do not agree on capacity (63–105 mAh over 6 sheets), cutoff (1.2–1.3 V over 6 sheets), volume (0.25–0.38 cc over 7 sheets) and impedance (5 to 25 ohms over 5 sheets), so each figure is printed as the range the sheets give, not as one of them. Where one number is needed to rank or compare, the page uses the median of the sheets, 100 mAh.
The axis is the difference from this cell, not a range of volts: the centre is 1.55 V and the ruled middle is the class where a substitute still runs and only reads off — a gap within 20.0% of the higher of the two nominals, which counted from this cell reaches 20.0% below and 25.0% above. One gap, two readings: the other cell’s page prints the other figure for this same pair and lands on the same class. Outside those two rules the class changes. The middle is drawn straight and the outer fifth of each side is compressed, so -3.2% puts the mark in one place here and in the same place on every other page of this site.
One rung on a ladder of thicknesses
This is one rung of a ladder: 17 other cells share the 11.6 mm diameter and differ only in depth, running 1.6 to 10.8 mm against this one's 3.6. The nearest rung, LR54, is 3.1 mm — the same hole, less inside it.
What this cell can stand in for
7 designations Energizer no longer lists point at this cell as the closest thing it does list, and the voltage is not the same: in a device built for one of them this cell runs up to 14.8% off. The device will run, and an instrument calibrated for the old cell will read off.
Each row names a cell no longer made, with its own voltage and chemistry. Fit of this cell and Voltage of this cell describe this cell put in its place: whether it enters that compartment, and how far its voltage sits from the voltage the device was built for. The discontinued cell’s own page prints the same figure for the same swap.
| Discontinued cell | Its voltage | Fit of this cell | Voltage of this cell | Its chemistry |
|---|---|---|---|---|
| 201 | 1.5 V | drop-in | 1.55 V +3.3%close enough | silver oxide |
| MR42 | 1.4 V | drop-in | 1.55 V +10.7%reads off | mercuric oxide |
| MR43 | 1.4 V | sits lower | 1.55 V +10.7%reads off | mercuric oxide |
| NR43 | 1.4 V | sits lower | 1.55 V +10.7%reads off | mercuric oxide |
| NR44 | 1.4 V | sits lower | 1.55 V +10.7%reads off | mercuric oxide |
| PR43 | 1.4 V | sits lower | 1.55 V +10.7%reads off | zinc air |
| MR44 | 1.35 V | sits lower | 1.55 V +14.8%reads off | mercuric oxide |
What the chemistry changes
Everything above answers size and voltage. What it cannot answer is chemistry, and 2 other kinds are in play here beside the silver oxide this cell uses.
- Silver oxide holds its voltage almost flat until it is spent, which is why watches and light meters were built around it.
- Alkaline drops in voltage steadily as it empties, so a device calibrated for a flat discharge will drift as it goes.
- Zinc air takes oxygen from the air through the holes in its face. It starts discharging the moment the tab comes off and runs down in weeks whether the device is used or not, and a sealed compartment starves it.
What a watch movement does with this cell
A pack sold as a 344 watch battery is this cell. A quartz movement pulls a short pulse through the cell every second and reads the voltage between pulses. That is why the chemistry in this envelope matters more than the size does. Silver oxide holds 1.55 V nearly flat until it is spent.
MR42 is the same 11.6 x 3.6 mm in mercuric oxide and no longer listed: in a movement built for its 1.4 V this cell runs 1.55 V, +10.7%. The case cannot tell them apart; the movement can. Internal impedance 5 to 25 ohms, published by the maker. That is the figure the stepper motor pulse sees, and it rises as the cell ages. The nearest is SR54: it enters and sits lower and runs 1.55 V, same volts.
- 9 cells measure close enough to compare against it in the Energizer data this site reads, and 9 of them are still listed.
- By stored energy it stands anywhere from 1 to 2 of 2 in its envelope, at 98–163 milliwatt-hours, depending on which data sheet is read.
- Energizer files it for Europe and North America, which is where the part is sold rather than where the cell will work.
- The maker still lists it, under 4 product lines: 344, 344/350, 350 and 387S.
Drawn to scale
SR42, side elevation, from the published figures
The same scale for all of them. The dashed line marks the height of SR42: a silhouette that stops short of it will not reach the contact, one that crosses it will not let the cover close.
Every published figure
Every field the maker fills is filled for this one: 12 figures in all, from chemistry through to where it is sold.
| Designation | SR42 |
|---|---|
| Also stamped | 344, 344/350, 350, 387S |
| Chemistry | Silver Oxide |
| Nominal voltage | 1.55 V |
| Diameter | 11.6 mm |
| Height | 3.6 mm |
| Weight | 1.6 g |
| Volume | 0.25–0.38 cc |
| Capacity | 63–105 mAh to 1.2–1.3 V |
| Stored energy | 98–163 mWh |
| Energy density | 257–651 mWh per cc |
| Impedance | 5 to 25 ohms |
| In the Energizer catalog | Listed |
| Listed for | Europe, North America |
The IEC standard writes this designation in full as SR1136. That form comes from the standard, not from a record of the maker’s, which is why it is not among the markings above.
2 rows in the table are not the maker's but ours: stored energy and energy per cubic centimeter. Everything else is reproduced without change.
The number a pulse sees
Energizer publishes an impedance band of 5 to 25 ohms for SR42. It is the least quoted number on the sheet and the one that decides whether the cell can drive a pulse; 3 other published figures sit below.
The part occupies 0.25–0.38 cubic centimeters and weighs 1.6 g. Capacity and voltage together put 98–163 milliwatt-hours in that space. Energizer files it for Europe and North America.
- Internal impedance
- 5 to 25 ohms as published. A high-impedance cell sags under a pulse and recovers between pulses, which is what a movement or a sensor sees.
- Cutoff voltage
- 1.2 V. The published capacity is counted down to this voltage; a device that quits higher up sees less than the whole figure.
- Mass against volume
- 1.6 g filling 0.25–0.38 cubic centimeters. When the printing has worn off, a kitchen scale separates two cells of one envelope faster than a caliper does.
- Where the part is filed
- Europe and North America. That is a statement about the maker's distribution and not about where the cell works.
Is that a lot of energy?
Its place depends on which data sheet you trust. 98–163 milliwatt-hours by the sheets behind this page puts it anywhere from 1 to 2 of the 2 cells measured in this shell, because the sheets of this cell or of its neighbours print a range rather than one capacity.
A width the catalog keeps returning to
11.6 mm is a width this catalog keeps coming back to: 19 coins sit within half a millimeter of it, SR42 included.
9 of those ones are still listed. Its 257–651 milliwatt-hours per cubic centimeter sit above 32 to 98 percent of everything here that publishes both a capacity and a volume. 30 of the 79 coins share its 1.55 V exactly.
- CR1616 — the next step down by volume: 0.32 cubic centimeters against this cell's 0.25–0.38.
- CR1620 — the next step up by volume: 0.4 cubic centimeters against this cell's 0.25–0.38.
- 1177SO — 11.6 x 1.6 mm, 1.55 V, silver oxide.
- CR11108 — 11.6 x 10.8 mm, 3 V, lithium.
One figure the maker does not publish
One field is empty for SR42: operating temperature. A blank means the maker publishes no figure, which is not the same as zero, and it is the reason one comparison below is missing rather than wrong.
The blanks are the same in all 7 records behind this designation, so they are the catalog's silence and not a merge losing a value. What is not missing is the envelope: 11.6 x 3.6 mm, published and checked against the designation itself.
- No operating temperature — so this page cannot tell you whether the maker claims anything at all below freezing.
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 here is the figure for one swap: the voltage of the cell that goes in, measured against the cell the device was built for, and the figure belongs to the cell whose voltage is printed beside it. In the table of cells that fit in place of this one, and on the scale, that is each candidate against this cell: a cell that runs lower carries a minus, one that runs higher carries a plus, and a cell at the same nominal voltage carries zero. In the table of cells no longer made, it is this cell against each of them, because the swap goes into a device built for the old cell, and that cell’s own page prints the same figure for the same swap. Where cells still listed can each stand in for the other, those are different swaps: each page measures against its own cell, the sign is the other one, and the size can differ slightly, because one gap is a larger share of the lower voltage; 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.
Cells measured next to this one
1 cell sits at exactly this size, and 17 more share the diameter at other depths. The first group is interchangeable by measurement; the second is not.
- MR42 — 11.6 x 3.6 mm, 1.4 V
- 1177SO — 11.6 x 1.6 mm, 1.55 V
- 365 — 11.6 x 1.6 mm, 1.55 V
- SR55 — 11.6 x 2 mm, 1.55 V
- LR55 — 11.6 x 2.1 mm, 1.5 V
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.
Records that disagree behind this page
SR42 is assembled from 7 catalog records, and they do not agree with each other on every field. Both sides are numbered below so the disagreement can be read rather than taken on trust.
- [1] Energizer catalog record 114, listed as 344, active in the snapshot. Technical data sheet: 344z.pdf.
- [2] Energizer catalog record 147, listed as 387S, active in the snapshot. Technical data sheet: 387sz.pdf.
- [3] Energizer catalog record 489, listed as 344, obsolete in the snapshot. Technical data sheet: 344.pdf.
- [4] Energizer catalog record 491, listed as 344/350, obsolete in the snapshot. Technical data sheet: 344-350.pdf.
- [5] Energizer catalog record 496, listed as 350, obsolete in the snapshot. Technical data sheet: 350.pdf.
- [6] Energizer catalog record 555, listed as 387S, obsolete in the snapshot. Technical data sheet: 387s.pdf.
Every figure above is reproduced from those records without change; the comparisons are ours and are described on the method page. Snapshot: Energizer technical data, retrieved 1 September 2026.
Putting this on your own site, blog or repair page? The same answer without the site around it — fit, voltage, chemistry and the limits that go with them — is at /embed/sr42/. It loads nothing from anywhere else. Paste this wherever your editor accepts HTML; forums usually strip embedded frames, so on a forum link to this page instead:
<iframe src="https://batterycross.com/embed/sr42/" width="100%" height="520" loading="lazy" title="SR42 replacements"></iframe>