10 · Group Sizes
Car battery group sizes explained
The Battery Council International (BCI) group size defines a battery's physical dimensions, terminal position, and terminal type. It does not specify CCA or capacity, those vary by line within a group. Get the group size wrong and the battery will not fit the tray, the cables won't reach, or the hold-down clamp won't secure it.
BCI Chart · 10.1
Group size reference
Dimensions in inches, length x width x height. CCA range covers the typical product line within each group.
| Group | L (in) | W (in) | H (in) | CCA |
|---|---|---|---|---|
| 24 / 24F | 10.25 | 6.81 | 8.88 | 650 to 850 |
| 25 | 9.06 | 6.88 | 8.88 | 550 to 700 |
| 26 / 26R | 8.19 | 6.81 | 7.75 | 525 to 650 |
| 34 | 10.25 | 6.81 | 7.88 | 650 to 800 |
| 35 | 9.06 | 6.88 | 8.88 | 550 to 720 |
| 47 (H5) | 9.50 | 6.88 | 7.50 | 600 to 700 |
| 48 (H6) | 11.00 | 6.88 | 7.50 | 725 to 800 |
| 49 (H8) | 13.94 | 6.88 | 7.50 | 850 to 950 |
| 51R | 9.38 | 5.06 | 8.81 | 450 to 600 |
| 65 | 12.06 | 7.50 | 7.56 | 750 to 950 |
| 78 | 10.25 | 7.06 | 7.88 | 650 to 800 |
| 94R (H7) | 12.40 | 6.88 | 7.50 | 800 to 950 |
Find yours
Four ways to find your group size
- 01
Read the label on your current battery
The group size is printed on the top, side, or sticker. Look for a 2 or 3-digit number, sometimes with a letter (24F, 51R, 94R).
- 02
Check the owner's manual
Most manuals list battery specs in the maintenance section. Look for terms like 'group size,' 'BCI,' or 'battery part number.'
- 03
Use an online fitment tool
AutoZone, O'Reilly, Advance, NAPA all have year/make/model finders that return the correct group size.
- 04
Measure the tray
If the battery is missing or aftermarket, measure the tray L x W x H in inches and cross-reference the BCI chart above.
Warning
What happens if you install the wrong group size
- · Battery may not fit the tray, leaving it loose and prone to vibration damage.
- · Reverse-polarity terminals (the "R" suffix) put positive on the wrong side; cables will not reach without modification.
- · Hold-down bracket may not clamp properly, voiding the warranty if the battery moves.
- · Side-post vs top-post mismatch means the cables physically cannot connect.
- · Lower CCA than the OEM spec causes hard cold-weather starts and shortened life.
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