Wrench / socket
10 mm
0.3937" / 10 mm across flats
Wrench
- Across flats
- 0.394" · 10.00 mm
- Nearest other system
- 3/8"−0.0187"
- Best substitute
- 7/16"Does not fit
Full chart 56 rows
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Wrench & socket size chart (SAE ↔ metric)
56 rowsWrench & socket size chart (SAE ↔ metric) · ScrewBoltChart
screwboltchart.com · inch-first · tap drills 75% (soft metals) · torque dry, K=0.20 · verify against the governing standard
| 0.1260" | 3.20 | 5/32" · Does not fit | #2, M1.6 | ||
| 0.1563" | 3.97 | 4 mm · Interchangeable | #0, #1, M2 | ||
| 0.1575" | 4.00 | 3/16" · Does not fit | #0, #1, M2 | ||
| 0.1875" | 4.76 | 5 mm · Loose: rounding risk | #2, #3, #4 | ||
| 0.1969" | 5.00 | 7/32" · Does not fit | M2.5 | ||
| 0.2165" | 5.50 | 7/32" · Interchangeable | M3 | ||
| 0.2188" | 5.56 | 6 mm · Does not fit | — | ||
| 0.2362" | 6.00 | 1/4" · Loose: rounding risk | M3.5 | ||
| 0.2500" | 6.35 | 7 mm · Does not fit | #4, #5, #6, #8 | ||
| 0.2756" | 7.00 | 9/32" · Interchangeable | M4 | ||
| 0.2813" | 7.14 | 8 mm · Does not fit | — | ||
| 0.3125" | 7.94 | 8 mm · Interchangeable | #5, #6, #10, #12 | ||
| 0.3150" | 8.00 | 11/32" · Does not fit | M5 | ||
| 0.3438" | 8.73 | 9 mm · Loose: rounding risk | #8 | ||
| 0.3543" | 9.00 | 3/8" · Does not fit | — | ||
| 0.3750" | 9.52 | 10 mm · Does not fit | #10 | ||
| 0.3937" | 10.00 | 7/16" · Does not fit | M6 | ||
| 0.4331" | 11.00 | 7/16" · Interchangeable | — | ||
| 0.4375" | 11.11 | 12 mm · Does not fit | #12, 1/4" | ||
| 0.4724" | 12.00 | 1/2" · Does not fit | — | ||
| 0.5000" | 12.70 | 13 mm · Loose: rounding risk | 5/16" | ||
| 0.5118" | 13.00 | 9/16" · Does not fit | M8 | ||
| 0.5512" | 14.00 | 9/16" · Loose: rounding risk | — | ||
| 0.5625" | 14.29 | 15 mm · Does not fit | 3/8" | ||
| 0.5906" | 15.00 | 19/32" · Interchangeable | — | ||
| 0.5938" | 15.08 | 16 mm · Does not fit | — | ||
| 0.6250" | 15.88 | 16 mm · Interchangeable | 7/16" | ||
| 0.6299" | 16.00 | 11/16" · Does not fit | M10 | ||
| 0.6693" | 17.00 | 11/16" · Does not fit | M10 | ||
| 0.6875" | 17.46 | 18 mm · Does not fit | 7/16" | ||
| 0.7087" | 18.00 | 3/4" · Does not fit | M12 | ||
| 0.7480" | 19.00 | 3/4" · Interchangeable | M12 | ||
| 0.7500" | 19.05 | 20 mm · Does not fit | 1/2" | ||
| 0.7874" | 20.00 | 13/16" · Does not fit | — | ||
| 0.8125" | 20.64 | 21 mm · Loose: rounding risk | 9/16" | ||
| 0.8268" | 21.00 | 7/8" · Does not fit | M14 | ||
| 0.8661" | 22.00 | 7/8" · Loose: rounding risk | M14 | ||
| 0.8750" | 22.23 | 23 mm · Does not fit | 9/16" | ||
| 0.9055" | 23.00 | 15/16" · Does not fit | — | ||
| 0.9375" | 23.81 | 24 mm · Loose: rounding risk | 5/8" | ||
| 0.9449" | 24.00 | 1" · Does not fit | M16 | ||
| 1.0000" | 25.40 | 26 mm · Does not fit | — | ||
| 1.0236" | 26.00 | 1-1/16" · Does not fit | — | ||
| 1.0625" | 26.99 | 27 mm · Interchangeable | M18 | ||
| 1.0630" | 27.00 | 1-1/8" · Does not fit | M18 | ||
| 1.1250" | 28.58 | 30 mm · Does not fit | 3/4" | ||
| 1.1811" | 30.00 | 1-3/16" · Loose: rounding risk | M20 | ||
| 1.1875" | 30.16 | 32 mm · Does not fit | — | ||
| 1.2500" | 31.75 | 32 mm · Loose: rounding risk | — | ||
| 1.2598" | 32.00 | 1-5/16" · Does not fit | M22 | ||
| 1.3125" | 33.34 | 34 mm · Does not fit | 7/8" | ||
| 1.3386" | 34.00 | 1-3/8" · Does not fit | M22 | ||
| 1.3750" | 34.92 | 36 mm · Does not fit | — | ||
| 1.4173" | 36.00 | 1-7/16" · Does not fit | M24 | ||
| 1.4375" | 36.51 | N/A · No larger size | — | ||
| 1.5000" | 38.10 | N/A · No larger size | 1" |
05 / Field guide
Thirteen
isn’t a half.
SAE and metric wrenches overlap just enough to be dangerous. A few pairs are true substitutes; most are close enough to slip on and round a nut. This chart shows which is which.
The fit rule
A wrench only works if it is at least as large as the nut. We call a substitute interchangeable when it is within 0.15 mm larger, loose up to 0.4 mm, and no good beyond that. 19 mm and 3/4" (19.05 mm) are interchangeable. 13 mm on a 1/2" nut is 0.3 mm loose. A 1/2" wrench will not fit a 13 mm nut at all.
gap = wrench − nut ≤ 0.15 mm ok · ≤ 0.40 mm loose · more = no
Which wrench a bolt takes
Inch: 1/4" bolts take 7/16", 5/16" take 1/2", 3/8" take 9/16" and 1/2" take 3/4". Metric ISO: M6 takes 10 mm, M8 13 mm, M10 16 mm (17 mm DIN) and M12 18 mm (19 mm DIN).
Six-point or twelve-point
Six-point sockets grip the flats and are less likely to round a tight or corroded nut. Twelve-point sockets are easier to place in tight spaces. Use six-point for breaking loose and final torque.
Open-end, box and adjustable
Open-end wrenches touch only two flats, so they slip and round nuts under high torque. Box-end wrenches and six-point sockets contact all six flats and carry far more torque. Adjustable wrenches are convenient but the moving jaw flexes; set it tight on the flats and pull toward the fixed jaw. For flare nuts on brake and fuel lines, use a flare-nut (line) wrench, which grips five flats.
Questions
Answered plainly.
01What size wrench is a 10 mm in SAE?+−
There is no exact SAE equal. 10 mm is 0.394"; 3/8" (0.375") is too small and 13/32" is uncommon. Use a 10 mm wrench.
02Is 19 mm the same as 3/4"?+−
Practically yes. 3/4" is 19.05 mm, only 0.05 mm larger, so a 3/4" wrench fits a 19 mm nut well and a 19 mm wrench fits a 3/4" nut snugly.
03Is 13 mm the same as 1/2"?+−
No. 13 mm is 0.512". It slips over a 1/2" nut with 0.3 mm of play, enough to round a tight nut. A 1/2" wrench won’t fit 13 mm at all.
04What wrench fits a 3/8" bolt?+−
A 9/16" wrench for a standard 3/8" hex cap screw and its finished hex nut.
05What wrench fits an M10 bolt?+−
16 mm for ISO 4032 nuts and ISO heads, 17 mm for older DIN 934 parts. Keep both.
06What size is 5/16" in mm?+−
7.94 mm. An 8 mm wrench fits a 5/16" hex nearly perfectly, 0.06 mm larger.
07What size wrench fits a 1/2" bolt?+−
A 3/4" wrench for a standard 1/2" hex cap screw and its finished hex nut.
08What wrench fits an M12 bolt?+−
18 mm for ISO 4032 parts and 19 mm for DIN 934 parts. Many hardware-store M12 nuts are still 19 mm.
09What is 9/16" in mm?+−
14.29 mm. A 14 mm wrench is too small to fit; 15 mm fits with 0.7 mm of play, which is too loose for a tight nut.
10What wrench fits an M6 nut?+−
A 10 mm wrench, for both ISO 4032 and DIN 934 M6 nuts. The M6 socket head cap screw takes a 5 mm hex key instead.
11Why do I have both 3/8" and 10 mm sockets?+−
They are 0.48 mm apart, too far to substitute. 3/8" is too small for a 10 mm nut, and 10 mm is loose enough on a 3/8" nut to round it.
12What is a 7/16" wrench in mm?+−
11.11 mm. An 11 mm wrench is too small to fit; a 12 mm wrench has 0.9 mm of play. Use the 7/16".