Free Engineering Tools
Fastener Calculators and Reference Charts
Free calculators, converters and charts for thread engagement, tap drills, bolt torque, fits and tolerances, hardness, corrosion and fastener sizes. Search below, or browse by job.
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Featured tool · Calculator
Torque & Preload Calculator
Calculate tightening torque and preload tension for hex head and socket head screws. Compare metric and inch systems and get the values needed to make a more informed fastening decision.
- Metric + Inch: Common fastener systems
- Torque + Preload: Both outputs together
- Application Ready: Quick engineering checks
Engineering resources
Most Popular Tools & Calculators
Calculator
Tap Drill Size Calculator
Find the correct drill-hole diameter before tapping. Supports common thread percentages.
Drill Diameter · Thread % · Metric + Inch
Calculator
ROI Calculator
Evaluate return on investment from fastener supply-chain consolidation.
Annual Savings · Payback · ROI
Calculator
Fastener Weight Calculator
Estimate fastener weight by type, size, length, material and quantity.
Weight · Material · Quantity
Converter
Hardness Conversion
Convert between Rockwell C, Brinell and Vickers hardness scales per ASTM E140.
Rockwell C · Brinell · Vickers
Converter
Metric–Inch Converter
Bridge metric and inch fastener specifications, property classes and dimensional equivalents.
Dimensions · Property Class · Grade Ref
Selection Tool
Fastener Grade Comparison
Compare property classes, materials and strength levels for fastener selection.
Strength · Material · Grade
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Not sure which fastener to use?
Answer four questions about your joint and get the fastener families that fit, with the reasons.
Geometry Tools
Layout calculators for hole patterns.
Reference Charts
Quick-lookup tables for sizes, grades, threads and materials.
Fastening Know-How
Online Calculators and Converters for Fasteners
Our calculators and converters are designed for engineers, technicians, industrial designers, and students involved in the development and assembly of bolted joints.
Manufacturing Unit Converters
Precision Factors for Global Standards
Convert inches, millimeters, centimeters, feet and meters. Now on the force conversion page.
Use the right moment of force. Our torque converter tool ensures precise conversion between units or unit systems.
Convert psi, bar, atmospheres, kPa and MPa. Now on the force conversion page.
May the (right) force be with you. This tool converts different force units and different unit systems.
Measure up to the challenge. Convert the most common hardness scales such as Brinell (HB), Rockwell (HR), and Vickers (HV).
Bridge the gap between metric and inch fasteners. Input thread type and size and the mechanical property class.
Thread Specifications & Hole Design
Shop-Floor Standards for Tapping & Forming
Accurately determine metric thread dimensions, ensuring correct fit, complying with standards, and meeting design and manufacturing requirements.
Determine the appropriate screw hole size for metric thread-forming screws.
Find out the correct tap drill size to determine the drill hole size before tapping for the most commonly used screws.
Calculate the optimal boss geometry for safe and easy screwing directly into various types of thermoplastics.
Identify the right tolerances for shafts and holes, based on standard tolerance classes, and limit deviations from ISO 286-2.
Work out the weight of round, hex and flat bar and fastener blanks in steel, stainless, aluminum and brass.
Bolt Torque & Assembly Tension
High-Certainty Joint Integrity Tools
Estimate the optimal dimension and strength a bolt should have for your application.
Calculate disc spring and Belleville washer force for a given deflection with the DIN 2092 method.
Assess the savings potential for fasteners by analyzing the total cost of ownership (TCO).
See where fastener cost sits beyond the piece price: logistics, quality, administration and inventory.
What is the minimum required thread engagement length for both blind-hole and through-hole applications? Calculate it
Calculate tightening torque and preload for hex head and socket head screws, considering various friction coefficients.
Determine the tightening torque, preload, and surface pressure for hex head, socket head, and countersunk screws – all with various options for special geometry and strength of the selected fastener.
Calculate tightening torque and preload and surface pressure for hex head and socket head screws.
See how the nut factor (K) and tightening-tool accuracy change the preload a given torque delivers, for inch and metric bolts.
Disclaimer
The engineering calculators are free to use under the terms and conditions. They are designed to facilitate and support you in product design and the results depend on the assumptions you provide. We do not guarantee their accuracy or applicability to your specific circumstances. Please contact us for thorough engineering advice.
Engineering FAQ: Assembly & Design Challenges
Why is Nut Factor (K) critical for bolt torque accuracy?
The Nut Factor is a summary variable for the total friction in a joint. Since 90% of torque is lost to friction, an incorrect K-factor leads to either insufficient clamp load (joint loosening) or excessive tension (bolt yielding). Verified K-factors are the only way to move from theoretical torque to actual preload certainty.
How does friction scatter impact high-performance fastener coatings?
Coating variations, such as inconsistent zinc plating, create a “scatter” range. If friction is lower than planned, standard torque will over-stretch and snap the hardware. Lubricants are often used to narrow this scatter to ±10%, ensuring more predictable clamp loads across different hardware batches.
What is the standard engagement length to prevent thread stripping?
For industrial reliability, the rule of thumb is 1.5 times the diameter (1.5d) for steel bolts in Aluminum and 2.0d for Plastics. This ensures the fastener fractures before the internal threads of the expensive component fail.
Can material hardness (HRC) predict a bolt’s tensile strength?
Partly. For carbon and alloy steel bolts, hardness tracks tensile strength closely enough that ISO 898-1 and SAE J429 publish a hardness range for every property class or grade (for example class 8.8 is about 22 to 32 HRC, class 10.9 about 32 to 39 HRC, class 12.9 about 39 to 44 HRC). A hardness test is therefore a quick screening check, and it is how head markings are verified in incoming inspection. It is not a substitute for a tensile or proof-load test: hardness says nothing about decarburisation, thread rolling, or heat-treatment defects below the surface, and the correlation does not hold for stainless or non-ferrous fasteners. Use hardness to screen, and the tensile test on the certificate to accept.
Why are forming tap pilot holes larger than traditional drill sizes?
Cutting taps remove material, but forming (roll) taps displace it. Because the material is pushed into the thread peaks rather than removed, a larger starting hole is required to prevent tap breakage and excessive internal stress. Our Pilot Hole Tool calculates these displacement ratios based on material ductility.
How do pressure ratings influence fastener diameter selection?
Internal pressure creates a separating force on gaskets and flanges. Fasteners must provide a clamp load that exceeds this force plus a safety factor. Accurate pressure unit conversion (PSI to MPa) is a prerequisite for calculating the required tensile stress area of the hardware.
What is the relationship between tool accuracy and preload scatter?
Even if friction is perfect, a ±4% click wrench or a ±10% pneumatic tool adds variance to the applied force. When friction scatter and tool inaccuracy are combined, the total preload variation can reach ±40%. Professional joints require calibrated tools to stay within safe engineering limits.
Managing a Safety-Critical Fastening Project?
Our calculators provide baseline benchmarks. For aerospace, medical, or heavy industrial joints, we provide ultrasonic preload verification and VDI 2230 design audits.