PlainBattery — Battery Cross-Reference Guide

6.8mm × 2.1mm Battery Equivalents

2 model(s) use the same nominal 6.8mm × 2.1mm outline. They span 1.5, 1.55V and Alkaline, SilverOxide, so physical fit alone does not prove that one can safely replace another. Compare the printed code, voltage, chemistry, and device requirements before buying.

Same-size model comparison

ModelVoltageChemistryCapacityNominal sizeCommon labels
LR6211.5VAlkaline12–15 mAh6.8mm × 2.1mmAG1
SR621SW1.55VSilverOxide18–23 mAh6.8mm × 2.1mm364, 363

Which same-size batteries can replace each other?

The checks below compare each pair by size, voltage, and chemistry. “Closest match” still requires confirmation of drain rating and terminals; “conditional” means the device manual decides; a voltage mismatch means the pair must not be substituted.

LR621 vs SR621SW

Conditional

The nominal voltage and size are close, but Alkaline and SilverOxide have different discharge behavior. Follow the device specification.

How to measure a battery with calipers

Battery dimensions are nominal and small manufacturing tolerances are normal. Dirt, a bent wrapper, raised terminals, or squeezing the jaws can shift a reading by a few tenths of a millimeter. Use the code on the old cell as the primary identifier and measurements as a check.

  1. Remove the battery and wipe the faces and edge clean. Do not measure it inside the holder.
  2. Close and zero the digital calipers, then measure the widest diameter without squeezing.
  3. Measure body thickness across the flat faces. Avoid raised button terminals or welded tabs.
  4. Repeat each measurement after rotating the cell. Treat about ±0.1–0.2 mm as normal measuring variation.
  5. Finally confirm the printed voltage and chemistry. Never select a replacement from dimensions alone.

Related battery comparisons

Review record and primary sources

Reviewed by PlainBattery Technical Review Desk on 2026-08-25. Checked: shared nominal dimensions, voltage and chemistry differences, pairwise replacement guidance.

No model-specific manufacturer sheet is linked yet; confirm this entry against the device manual before use.

Revision record: source citations and field-level review scope added September 11, 2026. See our sources and methodology and corrections policy.