Metric vs Standard Wrench Sets: Which Should You Choose?
Choose the system your fasteners use. Metric wrenches are sized in millimeters and standard (SAE) wrenches in fractions of an inch. If you work on a mix of cars, bikes, appliances and older American equipment, a combined set is the safer choice, because the two systems are close in size but do not swap.
CRAFTSMAN CMMT87220Best overall
EFFICERE MA-24PC-MULTI-COMBO-ESDrop-forged all-rounder
SK 025141118766Largest sizes in top fiveWhat metric and standard wrench sets actually are
A metric wrench set is sized in millimeters, such as 10 mm, 13 mm or 17 mm. A standard set, which most US shoppers also see called SAE or inch, is sized in fractions of an inch, such as 3/8, 1/2 or 9/16.
A "full" metric set is not a fixed industry definition. It usually means a run of consecutive or near-consecutive millimeter sizes from a small size up to a large one, with few or no gaps. One maker's full set can cover 6 mm to 32 mm, while another's stops much sooner, so always read the size list rather than the label.
Most sets in this category are combination wrenches. One end is an open end and the other is a closed box end, both in the same size. That is why a single wrench covers a nut and gives you two ways to turn it.
Metric vs standard: which one fits your work
The right pick depends on what you fix. Many modern cars, motorcycles, bikes and imported appliances use metric fasteners. Older American vehicles, some plumbing and a lot of US-made equipment use inch sizes. Plenty of garages and homes contain both.
The two systems overlap closely, which is the trap. A 3/8 inch wrench is about 9.5 mm, and a 1/2 inch wrench is about 12.7 mm, so neither lines up cleanly with a 10 mm or 13 mm fastener. A near fit can round the corners of a nut. Use the exact size every time.
Our best combination wrench set page shows that most of the listed sets pair both systems, and only one compact roll is metric only, running from 8 mm to 22 mm. Anyone who owns both kinds of fasteners would need a second set with that one.
| Option | Best for | Watch out for |
|---|---|---|
| Metric only | Cars, bikes and electronics built to metric standards | Inch fasteners need another set |
| Standard (SAE) only | Older American equipment and some plumbing | Metric fasteners need another set |
| Combined SAE and metric | Mixed work, shared garages, first toolkits | Larger case and more pieces to keep in order |
Why metric wrench sets skip sizes
Sets are built around the sizes people reach for most. Skipping a rarely used size keeps the roll or case smaller and lighter, and it lets a maker offer a lower piece count.
You can see this in the published size lists. The EFFICERE 24-piece set lists metric sizes of 8, 10, 11, 12, 13, 14, 15, 17, 18, 19, 21 and 24 mm. That list jumps over 9, 16, 20, 22 and 23 mm. The HORUSDY 26-piece set has a similar pattern, with no 16 mm in its metric run.
The catch is that a missing size can stop a job. If your fastener happens to be a skipped size, you cannot make do with the nearest wrench without risking a rounded nut. Before you buy, compare the size list to the fasteners you already own.
Can you get a set with no skipped sizes?
Yes, though you usually trade size and weight for the extra coverage. Larger sets list long unbroken runs. The SK 42-piece set covers metric 6 mm through 28 mm one millimeter at a time, then adds 30 mm and 32 mm. The HORUSDY 32-piece set lists metric 7 mm through 22 mm with no gaps, plus 16 SAE sizes in finer steps such as 9/32 and 19/32.
The VEVOR 44-piece set also runs from 6 mm to 32 mm. It is the heaviest model in our comparison at 18.36 lb, so a set with this much coverage is not one you want to carry around all day.
If you want no gaps, look for these signs in the listing:
The other route is to buy a compact set and add single wrenches later for the sizes you actually need. That works well when you know your fasteners. You can see more options on our combination wrench set comparison.
- A full size list that shows every millimeter, not just a range like "6 to 32 mm"
- A piece count that matches the number of sizes you expect
- Both SAE and metric runs listed separately
- A case or pouch that holds every wrench in order so a missing one is easy to spot
How to choose in four steps
Use this short routine to settle the question for your own garage or toolbox.
- Check the fasteners you work on most. Note whether they are metric, inch or both.
- Write down the sizes you use most and compare them to each set's size list.
- Choose combined sets if your work mixes systems, and a single-system set if it does not.
- Pick a storage format you will actually use. A roll-up pouch is compact, while a hard case protects the wrenches and shows what is missing.
Features that matter beyond the size system
Once the size system is settled, a few details decide how the set feels. A 12-point box end engages a fastener at more angles, which helps in tight spots. A six-point design grips the flats better on stubborn nuts. A 15 degree offset lifts the handle so your knuckles clear the work.
Ratcheting wrenches save time on long runs of bolts. The CRAFTSMAN 20-piece set lists a 90-tooth ratcheting box end, and the ELEAD 33-piece set lists 72 teeth, with sizes stopping at 19.05 mm. Ratcheting adds moving parts and these sets do not reach the largest sizes, so check the top size against your biggest fastener.
Safety when using wrenches
Wrenches look simple, but slips cause skinned knuckles and worse. Pull the wrench toward you rather than pushing it, and make sure it sits fully on the fastener before you apply force. Wear safety glasses when working under a vehicle or on rusted bolts, since debris and flakes can fall into your eyes.
Do not use a wrench on live electrical parts. Disconnect the battery or switch off the power at the breaker first. Never slide a pipe over a wrench handle for extra leverage unless the maker says that is allowed, because it can break the tool or slip suddenly. If you are working on a jacked-up vehicle, support it with proper stands before you get underneath.
Frequently asked questions
Is standard the same as SAE?
In US tool shops, yes. Standard wrenches are sized in inches and fractions of an inch, and SAE is the common name for that system.
Can I use a metric wrench on an inch bolt?
It is better not to. Some sizes are close, but a near fit can round the corners of the fastener. Use the exact size or a wrench built for it.
Do I need both sets for basic home repairs?
Not always. If everything you fix is one system, a single set is enough. If you work on mixed items such as cars, furniture and appliances, a combined set saves a second purchase.
What does a combination wrench set include?
Each wrench has an open end on one side and a box end on the other in the same size. Sets vary in piece count, size range and storage.
How do I keep my wrenches organized?
Return each wrench to its slot after use. A roll-up pouch or a rack with labeled slots makes it easy to see which size is missing.