Alkaline LR and silver-oxide SR button cells can occupy the same physical envelope, but they are different electrochemical families. “Fits” therefore does not mean “direct replacement”.
The visible differences
The LR44/A76 record is nominally 1.5 V alkaline. Same-size SR44SW/303 and SR44W/357 are nominally 1.55 V silver oxide and preserve separate drain classes. Close voltage numbers do not make these one electrical product.
Silver oxide is commonly selected for stable watch and instrument service. Alkaline products are general-purpose and normally have a more sloping voltage profile. The device circuit, cut-off and expected service determine whether a substitution is acceptable.
A safe comparison sequence
First confirm that diameter and height match. Second compare the full nominal voltage and chemistry. Third inspect drain guidance and any W/SW suffix. Finally follow the device manufacturer’s current requirement.
LR44 versus either SR44 drain class: same 11.6 × 5.4 mm envelope, different chemistry and nominal voltage.
LR626 versus SR626SW: same 6.8 × 2.6 mm envelope, different chemistry and drain context.
LR1130 versus SR1130: same nominal size, different chemistry.
How Battery Codebook labels the relationship
Same-size LR/SR pairs receive a conditional-substitute verdict. That label deliberately prevents an unqualified equivalence claim while still explaining why retailers and users often cross-reference the codes.
Capacity cannot settle the question because published capacity depends on load, temperature and cut-off voltage.
How the discharge profile affects the decision
Two new cells can begin near similar voltages yet deliver different voltage behaviour over service. A circuit with a particular cut-off point may therefore show different usable life or indication behaviour even when both cells physically fit.
Battery Codebook avoids predicting runtime from chemistry alone. It exposes the distinction so the device requirement, not a generic cross-reference, controls the decision.
Three same-envelope clusters
At 11.6 × 5.4 mm, compare LR44 alkaline with SR44SW/303 and SR44W/357. At 6.8 × 2.6 mm, compare LR626 with SR626SW or SR626W. At 11.6 × 3.05 mm, compare LR54/LR1130 with the SR1130 watch families.
Each cluster explains why a shop may present alternatives together. None justifies calling the alkaline and silver-oxide records identical.
What to check on the device
Look for the complete printed battery designation in the compartment, manual or current manufacturer support material. If a watch movement specifies a W or SW silver-oxide code, keep that suffix. If it specifies an alkaline LR code, do not assume a chemistry change is approved.
When the requirement cannot be found, present the alternatives as unresolved rather than promising fit or performance.
Substitution checklist
A defensible LR-to-SR decision records the exact codes, confirms the envelope, compares 1.5 V alkaline with 1.55 V silver oxide, and checks drain guidance. It then looks for explicit permission in the device or movement documentation. Without that final evidence, the result remains conditional even if users commonly report that the alternative works.