CHECK THE BOLT
Make sure the diameter, thread pitch, and strength grade match your bolt. The size stamped on a socket isn't the bolt size.
GENERAL FASTENER REFERENCE
TORQUEBASE
Find general torque estimates for common SAE and metric bolts by size and grade. Use the quick lookup, browse the charts, or get printable PDFs for the shop.
GENERAL FASTENER TORQUE REFERENCE — NOT AN OEM SPECIFICATION
These values are estimates for general-purpose steel fasteners. They depend on the assumed bolt strength, clamp load, and friction. Do not use them for engine internals, wheels, brakes, steering, suspension, torque-to-yield bolts, or other critical assemblies. Use the manufacturer's tightening procedure whenever one is specified.
CHARTS & REFERENCES / INTERACTIVE TOOL
BOLT TORQUE FINDER
SAE + METRIC
SELECT YOUR BOLT
Not sure what bolt you have?
Check the size
Measure the outside of the threads, not the bolt head. For SAE bolts, count threads per inch. For metric bolts, measure the distance between threads in millimeters.
Check the grade
Grade 5 hex bolts commonly have three radial marks on the head; Grade 8 usually has six. Confirm the marking and fastener type before selecting a grade.
Still unsure?
SocketFinderUSA's Measured Bolt Finder can help with diameter and pitch, but measurements alone cannot confirm a bolt's strength grade. Don't guess if the markings are missing or unclear.
TORQUE ESTIMATES
3/8-16 · SAE Grade 5
DRY ESTIMATE
—
Assumes K = 0.20
LUBRICATED ESTIMATE
—
Assumes K = 0.15
Both estimates assume the same bolt preload, but different friction. Neither is a manufacturer tightening specification.
GENERAL REFERENCE ONLY — These modeled estimates are not certified installation torques. Check the fastener, joint and manufacturer procedure.
How were these values calculated?
The simplified model is T = K × F × d, using 75% of assumed nominal proof load as the target preload. The dry and lubricated estimates use K = 0.20 and K = 0.15 respectively. Actual friction can differ substantially with coating, surface finish, lubricant, washers and joint design.
These are engineering-model estimates, not installation instructions. Complete controlled-standard review and independent engineering signoff have not been obtained.
CHARTS & REFERENCES
SAE & METRIC TORQUE CHARTS
Find general torque estimates by bolt size and grade. Dry and lubricated values are shown separately.
READING THE CHART
BOLT SIZEThread diameter and pitch, not socket size.
GRADE / CLASSThe fastener's strength classification.
DRY / LUBRICATEDDifferent modeled friction conditions, not universal installation instructions.
Check diameter, thread pitch and grade. These calculated general-fastener estimates are not OEM tightening specifications.
SAE / INCH TORQUE CHART Grades 5 & 8 · UNC / UNF
All estimates in lb-ft (pound-feet)
GENERAL REFERENCE ESTIMATES
BOLT GRADE
THREAD TYPE
Check the bolt size, pitch and grade before referring to any torque value. Dry/lubricated assumptions use modeled nut factors K = 0.20 / 0.15.
METRIC TORQUE CHART Classes 8.8, 10.9 & 12.9 · Coarse / fine
All estimates in N·m (newton-metres)
GENERAL REFERENCE ESTIMATES
BOLT PROPERTY CLASS
THREAD TYPE
Metric pitch is the distance between neighboring thread crests in millimeters. A different pitch requires a different entry. Dry/lubricated assumptions use modeled nut factors K = 0.20 / 0.15.
Estimates, not installation instructions. Actual friction, female threads and joint strength can limit suitable torque. Use manufacturer specifications for the assembly.
PRINTABLE TORQUE CHARTS
SAE or Metric: $1.99 for 2 PDFs. Complete Set: $2.99 for all 4. Each chart includes 8.5×11 and 11×17 versions.
Digital downloads only. Calculated general-purpose estimates, not OEM specifications or joint-validated tightening instructions. Downloadable PDFs are currently supplied in English.
FASTENER BASICS
BEFORE YOU USE THE CHART
A few things worth checking before choosing a torque value.
CHECK THE THREADS
Oil, anti-seize, coatings, and washers affect friction. That changes the clamping force you can get at the same torque.
CHECK THE JOINT
A stronger bolt doesn't mean the threaded hole or the parts being clamped can handle more force. The joint matters too.
TECHNICAL INFORMATION
HOW WE CALCULATE THESE ESTIMATES
The chart starts with the bolt's size and strength grade, then estimates the torque needed to reach a modeled preload. Actual tightening torque also depends on the threads, surface finish, lubrication, and the joint itself.
THE BASIC METHOD
T = K × F × d
T = estimated tightening torque · K = assumed nut factor · F = modeled bolt preload · d = nominal bolt diameter.
The model targets 75% of nominal proof load. That's a model assumption, not a safe preload for every assembly.
DRY MODEL
K = 0.20
Assumed nut factor
LUBRICATED MODEL
K = 0.15
Assumed nut factor
Important: “Dry” and “lubricated” describe calculation assumptions, not universal installation conditions. Different coatings, oils, washers, and joint designs can give very different clamp loads at the same torque.
Calculation steps & formulas
The bolt's tensile stress area is used to estimate proof load. The model takes 75% of that load as the target preload, then applies the chosen nut factor.
SAE stress area ≈ π/4 × (d − 0.9743 / TPI)² (in²)
Metric stress area ≈ π/4 × (d − 0.9382 × pitch)² (mm²)
Target preload = stress area × proof stress × 0.75
Estimated torque = K × target preload × nominal diameter
Imperial input yields lb-in before conversion to lb-ft; metric input yields N·mm before conversion to N·m. The results use one calculation source for both the Finder and the charts. Conversions use the unrounded result; display values are rounded for readability.
Bolt strength values used by the model
These are the nominal proof-stress inputs used by the calculator, not a list of approved installation torques. These nominal bands do not cover every bolt geometry, length or material condition. Confirm the actual fastener standard and joint requirements.
SAE / Inch psi
| Grade | Modeled proof stress |
|---|---|
| 5 | 85,000 through 1 in |
| 8 | 120,000 |
Metric MPa
| Class | Modeled proof stress |
|---|---|
| 8.8 | 580 through M16; 600 above M16 |
| 10.9 | 830 |
| 12.9 | 970 |
These simplified bands may not cover every fastener configuration. A selected grade alone does not confirm the actual bolt material or joint suitability.
References & source notes
The documents below provide engineering background on fastener design and torque–tension behavior. Listing them does not mean they validate or endorse every estimate on this page.
- NASA Fastener Design Manual — general bolted-joint design background
- NASA-STD-5020A — technical standard for threaded fastening systems
- Fastenal: Torque–Tension Relationship — friction and torque–tension considerations
Review limits: The nominal inputs were numerically cross-checked against published technical data. Complete proprietary-standard clause review and qualified independent engineering signoff have not been obtained. These references do not certify installation torque.
Reference limits
This simplified model is for general-purpose steel fasteners. It is not a certified torque specification or an OEM procedure. Complete controlled-standard review and independent engineering signoff have not been obtained. Unknown grades, specialty fasteners and critical assemblies need their own specifications.
MEASURE · MATCH · WORK