Car battery size chart: BCI group size lookup

Battery group size chart

All 101 twelve-volt groups in Battery Council International’s car and light truck, heavy-duty commercial and general-utility tables. Dimensions are BCI’s maximum overall length × width × height, in the millimetres and inches BCI prints. The positive-terminal side is read off BCI’s assembly drawings: seen from above with the terminal edge nearest you, or for side-terminal groups, looking at the terminal face.

“Also called” is BCI’s own DIN and EN cross-reference, which BCI labels a best-fit estimate. Group 75’s height includes raised quarter covers; BCI says flat-top models are about 3/8 inch (10 mm) lower. Group 4D, 6D and 8D batteries carry both terminals on one short end. Six-volt, golf car, tractor, marine and floor-scrubber groups are left out.

What battery makers actually publish

BCI gives a maximum; real batteries in the same group differ by a few millimetres, and a few are listed over BCI’s figure. These are the published product dimensions from Interstate Batteries, Deka Batteries (East Penn) and ODYSSEY Battery (EnerSys), in mm (Interstate publishes inches; we converted). Where a maker sells several models in a group, the range is shown. ODYSSEY’s height is its maximum total height with terminals; Interstate and Deka do not say whether theirs includes the terminals.

Two readings of the table. Group 24 is where makers spread most: BCI gives 260 mm as the maximum length, Interstate’s MTP-24 is 260 mm, and Deka and ODYSSEY list 273 and 277 mm. And height is the least consistent figure, so if your hood or hold-down clamp is tight, use the exact model’s height, not the group’s. Interstate’s MTP-151R is left out: its published length and height look transposed against BCI’s.

Dual-terminal batteries

OPTIMA Batteries explains that group 34 has top terminals and 78 side terminals on a case of the same size, so one battery can carry both: its 34/78 measures 10.06 in long, 6.94 in wide and 7.88 in tall, slightly wider than a 34 because of the side terminals. The same page notes that group numbers starting with a 7 indicate side terminals.

• 34/78: OPTIMA REDTOP / YELLOWTOP 34/78, 10.06 × 6.94 × 7.88 in (256 × 176 × 200 mm, converted)
• 34/78: Deka 9A78DT, 778DT, 10 3/4 × 6 7/8 × 8 in (273 × 175 × 203 mm)
• 35/85: Deka 9A35/85, 9 9/16 × 6 3/4 × 7 3/4 in (242 × 171 × 197 mm)
• 75/86: Deka 675DT, 9 3/4 × 7 × 8 1/8 in (248 × 178 × 206 mm)
• 42/58R: Deka 642/58R, 542/58R, 10 × 7 1/4 × 6 7/8 in (254 × 184 × 175 mm)

How to read the terminal layout

• Which side is positive. BCI draws each group from above with the terminal edge nearest you. Group 24, 27, 34, 65 and 86 put the positive post on the left; 24F, 27F, 35, 51R and the H-series (47, 48, 49, 94R) put it on the right.
• The R suffix is the reversed-terminal version of a base group: 26 and 26R, 34 and 34R, 51 and 51R share a case size in BCI’s table but swap the posts (24R is listed 4 mm taller than 24). It is not a universal code. Group 35 is positive-right with no R, and 148 is BCI’s reversed 48 (H6).
• The F suffix groups (22F, 24F, 27F, 29NF) are drawn with ledges on the short ends of the case and the positive post on the right.
• Post type. SAE top posts are BCI type A; DIN (A1), EN/JIS (A2) and JIS pencil posts (A3) are the other top-post standards BCI lists, and BCI notes some JIS-sized original posts may need a connector change. Side terminals (type S) are threaded sockets in the case face.

Why it matters: Clarios says the wrong orientation can make cable connections difficult or impossible, and a battery that is too large or small may not secure properly in the tray.

How to measure a car battery

1. Look for the group number first. Clarios says to check the old battery’s label. OPTIMA Batteries warns that a part number can be completely unrelated to the battery’s size, so read the field marked “Group”.
2. Length is the longest side of the case at its widest point, including any hold-down ledges at the ends.
3. Width is the short side, front to back.
4. Height to the top of the terminals. BCI’s figures are maximum overall dimensions; ODYSSEY publishes both a total height with terminals and a lower container height, 0.5 to 0.8 inch apart on its group 24, 27, 34 and 65 batteries.
5. Note the positive post. Stand with the terminal edge nearest you and see which side carries the plus sign, then pick top posts or side terminals.

Measure the battery while it is in the car if you can; it is heavy and lead-acid batteries contain acid. Our guide to testing a car battery covers whether it needs replacing at all.

How the lookup works

• By group: the number you type is matched to BCI’s table, or to BCI’s DIN/EN alias (H6, T5 and so on). An alias that BCI maps to two groups, such as T5 (42 and 90), asks you to pick.
• By measurement: every group with your terminal type is compared with your length, width and height in millimetres. Length and width weigh most, because they decide whether the battery fits the tray; height counts half, because makers’ heights vary with terminals and handles; a group whose positive post is on the other side is pushed down the list and labelled. “Close” means within 12 mm on length and 8 mm on width.
• Chargers: picks are the ranked chargers whose chemistry, as summarised in our spec table, lists your battery type. Where a maker states an Ah range, it is compared with BCI’s original-equipment Ah reference for the group, when BCI gives one.
• No vehicle database. We do not map cars to groups; your owner’s manual, the old battery’s label or a maker’s battery finder does that.

Sources

Last checked: October 26, 2026. Each page or PDF was opened and read; figures are quoted as published.

1. Battery Council International: BCI group sizes: assembly numbers, dimensional specifications and ratings (PDF)Maximum overall L × W × H in mm and inches for every group, post/terminal type, assembly figure (terminal positions), OE CCA and Ah reference ranges, and the DIN/EN and JIS cross-reference charts.
2. Deka Batteries (East Penn): Complete battery line specifications, Form 2740 Rev. 1/25 (PDF)Length, width and height in inches and mm for each Deka AGM, EFB and flooded automotive battery, by group, including dual-terminal 34/78, 35/85, 75/86 and 42/58R models.
3. Interstate Batteries: Product specifications, e.g. MTX-24FLength, width and height for each MTP (flooded) and MTX (AGM) model; each model in the maker table links to its own page.
4. ODYSSEY Battery (EnerSys): ODYSSEY battery specificationsLength, width, maximum total height (with terminals) and maximum container height for Performance and Extreme series batteries.
5. OPTIMA Batteries: What does battery group 34/78 mean?Its 34/78 measures 10.06 in long, 6.94 in wide and 7.88 in tall; group numbers starting with 7 indicate side terminals, those starting with 2 or 3 top terminals.
6. OPTIMA Batteries: What is a group 34/78 battery?Some vehicles take a 78 but not a 34 (height clearance over top terminals), and some a 34 but not a 78 (width).
7. OPTIMA Batteries: What battery size is 8020-164?A maker's part number can be unrelated to the battery's group size.
8. Clarios: Car battery group sizeGroup size covers dimensions, terminal placement and fit; wrong terminal orientation can make cable connections difficult or impossible; check the old battery's label.