Battery Terminal Nut Size Guide
Most motorcycle battery terminals in these listings take M6 bolts with 11 by 8 by 4 mm square nuts, and this guide shows how to match the length, pitch and washers.
On this page
A motorcycle that will not start on a cold morning often comes down to a loose connection at the battery, and a missing terminal bolt turns a quick job into a hunt through the parts bin. Battery terminal nut size is the measurement that ends the hunt: match the thread, the nut and the length to the terminal, and the bolt seats the first try. This guide explains what each measurement means and how the hardware kits in the listings compare.
As an Amazon Associate I earn from qualifying purchases. GarageToolHQ earns a commission when you buy through links on our product pages, at no extra cost to you. Read our affiliate disclosure.
Motorcycle Battery Terminal Nuts and Bolt Kit
A 20-pack kit with 20 stainless steel bolts and 20 square nuts in M6 by 16 mm, with a 1 Year manufacturer warranty.
Pros
- 20 bolts and 20 square nuts cover many terminals
- M6 by 16 mm bolts with 8 by 11 by 4 mm square nuts
- 304 stainless steel and carbon steel with zinc plating are stated
- 1 Year manufacturer warranty is stated, the only warranty term here
Cons
- Inch figures do not match the metric figures: 4 mm is listed as 0.55 inches
- Only 16 mm length is stated
- No washers are stated
- No hex head or drive size is stated
Tnisesm 72PCS Battery Terminal Motorcycle Bolts
A 72-piece kit with M6 bolts in 10, 12, 16, 18 and 20 mm lengths and 36 square nuts, in 304 stainless steel.
Pros
- Bolts in 10, 12, 16, 18 and 20 mm lengths cover the widest range here
- 36 bolts and 36 square nuts, the most pieces here
- 304 stainless steel with rust, corrosion and oxidation resistance stated
- Square nut size is stated in mm and inches: 11 by 8 by 4 mm
Cons
- The 'You Will Get' line lists a 14 mm length the title and size line do not
- No warranty term is stated
- No washers are stated
- No hex head or drive size is stated
binifiMux 6-Pack Motorcycle Battery Terminal M6
A 6-pack kit with M6 by 16 mm bolts, spring and flat washers and 11 by 8 by 4 mm square nuts, in stainless steel A2-70.
Pros
- Spring washer and flat washer are included on the bolt
- Stated for an 8 AWG inverter cable or SAE battery connector
- Bolt is stainless steel A2-70, nut is carbon steel with a zinc finish
- Driven by a #3 Phillips bit, per the listing
Cons
- Only M6 by 16 mm is stated, with no other length
- No warranty term is stated
- Flat washer is not removable from the bolt
- No hex head size is stated
QIATOL 6 PCS Motorcycle Battery Bolts
A 6-piece kit with M6 by 16 mm carbon steel bolts and 11 by 8 by 4 mm square nuts, with a stated 1.0 mm pitch.
Pros
- Thread pitch of 1.0 mm is stated, the only pitch figure here
- Hex head fits a 10 mm spanner, per the listing
- Carbon steel with corrosion resistance stated
- Small stated size: 0.77 by 0.24 by 0.24 in
Cons
- Only 6 bolts and 6 nuts
- Only M6 by 16 mm is stated, with no other length
- No warranty term is stated
- No washers are stated
Battery terminal nut size: the quick answer
The listings here use M6 bolts with 11 by 8 by 4 mm square nuts: a coarse 6 mm thread, a 1.0 mm pitch and a hex head that fits a 10 mm spanner on the QIATOL kit. Bolt lengths run from 10 mm to 20 mm, with 16 mm the only length stated in 3 of the 4 kits. The table below puts the 4 kits side by side.
| Kit | Bolt sizes | Square nut | Pieces |
|---|---|---|---|
| bestune 20 Pack | M6 by 16 mm | 8 by 11 by 4 mm | 20 bolts, 20 nuts |
| Tnisesm 72PCS | M6 by 10, 12, 16, 18, 20 mm | 11 by 8 by 4 mm | 36 bolts, 36 nuts |
| binifiMux 6-Pack | M6 by 16 mm | 11 by 8 by 4 mm | 6 bolts, 6 nuts |
| QIATOL 6 PCS | M6 by 16 mm | 11 by 8 by 4 mm | 6 bolts, 6 nuts |
Step 1: Read the thread size
Start with the thread. The QIATOL listing states it plainly: a coarse 6 mm thread, a 1.0 mm pitch, a 16 mm screw length and a hex head that fits a 10 mm spanner. Every kit here is M6, so the thread is the same across the 4 listings, and the choice comes down to length, washers and count. If the old bolt is still in the parts bin, match the new bolt to its thread before ordering, since an M6 nut will not seat on a different thread.
Step 2: Match the square nut
The square nut is the part that sits in the terminal slot, and its size is the same in 3 of the 4 kits: 11 by 8 by 4 mm, stated as 0.43 by 0.31 by 0.16 in on the Tnisesm listing. The bestune kit states its nut as 8 by 11 by 4 mm, the same figures in a different order, but lists the inches as 0.31 by 0.43 by 0.55 inches, and 4 mm is 0.16 in, not 0.55 in, so the bestune inch figure reads as a listing error. A nut that is too thick for the slot will not sit flat, and a nut that is too thin will turn in the slot, so check the metric figures against the slot before ordering. For more on terminal shapes, see the types of battery terminals guide.
Step 3: Pick the bolt length
Length is where the kits differ most. The Tnisesm kit states M6 bolts in 10, 12, 16, 18 and 20 mm, the widest stated range here, while the other kits state M6 by 16 mm only. The Tnisesm listing has one wrinkle: its “You Will Get” line lists 6 pieces each of M6 by 10, 12, 14, 16, 18 and 20 mm, but the title and the size line list no 14 mm length, so the 14 mm bolts may or may not be in the box. A 16 mm bolt suits the terminals in these listings, and a longer bolt suits a terminal with a thicker lug or a stacked cable, so measure the terminal and the cable lug together before picking a length.
Step 4: Check the washers and the drive
Washers and drive decide how the bolt goes in. The binifiMux kit is the only one here with washers stated: a spring washer and a flat washer on each bolt, with a flat washer diameter of 11.6 mm and a thickness of 1.5 mm, and the flat washer is not removable from the bolt. Its screw head is 9.8 mm wide and 4 mm thick, and the bolt is driven by a #3 Phillips bit. The QIATOL kit is driven by a 10 mm spanner on a hex head instead. The bestune and Tnisesm kits state no washer and no drive size, so check the listing before assuming the bolt matches the tools on the bench.
The terminal hardware kits
Each kit below handles a different part of the sizing job, from the widest length range to the only stated washers and the only stated warranty.
Lead-acid batteries can release hydrogen while charging, so charge in a ventilated space away from sparks and flames, connect positive first and negative last, set the charger to the battery type (flooded, AGM, gel, lithium), and wear eye protection. Read our Safety Disclaimer.
How the points were given
The Shop Score weighs performance, build, value, safety and warranty. For terminal hardware, performance covers the stated sizes and how completely the kit covers the sizing job, build covers the stated materials, and value weighs the stated pieces against the other kits here. Safety covers stated safety-relevant features, and no kit here states a certification, so safety scores zero for all 4. Warranty covers the stated term, and only the bestune kit states one, a 1 Year manufacturer term. How we pick explains the weights.
FAQ: garage tools
What size is a motorcycle battery terminal nut?
The listings here use an 11 by 8 by 4 mm square nut with M6 bolts, stated as 0.43 by 0.31 by 0.16 in on the Tnisesm listing. The bestune kit states the same nut as 8 by 11 by 4 mm.
What thread pitch do battery terminal bolts use?
The QIATOL listing states a coarse 6 mm thread with a 1.0 mm pitch, and a hex head that fits a 10 mm spanner. No other kit here states a pitch figure.
What length battery terminal bolt do I need?
The kits here state M6 bolts from 10 mm to 20 mm, with 16 mm the only length stated in 3 of the 4 kits. Measure the terminal and the cable lug together, then pick a length from the stated range that seats the nut fully.
Do battery terminal bolts come with washers?
Only the binifiMux kit here states washers: a spring washer and a flat washer on each bolt, with a flat washer diameter of 11.6 mm and a thickness of 1.5 mm. The bestune, Tnisesm and QIATOL kits state no washers.
What size wrench fits a battery terminal bolt?
The QIATOL kit states a hex head that fits a 10 mm spanner, and the binifiMux kit states a #3 Phillips bit drive. The bestune and Tnisesm kits state no drive size.
Related: types of battery terminals, the best ring terminals for car batteries, our battery terminal connectors and the diagnostics and electrical hub. Also see how to clean corroded car battery terminals and the best dielectric grease for battery terminals.
