Inputs
Results
ΔF ≈ (kb·kj/(kb+kj)) × ΔL. ΔL comes from the angle and pitch.
What this calculator actually solves
Torque-to-yield (TTY) is the modern way to spec head bolts: torque to a snug value, then rotate the bolt an additional angle. The angle is specified by the manufacturer because the actual preload depends on the bolt's stiffness relative to the joint's stiffness — which depends on the geometry, not just the bolt size.
This calculator lets you back out the effective clamp load from a target angle, and shows you whether your fastener stiffness assumptions match the spec.
Who this is for
Engine builders working on engines that spec TTY bolts (most modern DOHC engines, many modern diesel head bolts).
Restoration shops dealing with multi-piece head bolts where the angle is the only way to get repeatable preload.
How to read the results
A preload that's within 5% of your target spec means your stiffness assumption is correct. If it's off by more than 10%, re-check the joint stiffness — usually the gasket compliance is the biggest variable.
Limitations
Stiffness values change with bolt elongation, gasket crush, and thermal expansion. The numbers here are at room temperature; under operating heat, bolt load drops 10–20%.
Frequently Asked Questions
Why TTY instead of torque?
Because torque-to-yield achieves much more repeatable preload. Friction variability makes a torque-only spec accurate to ±25%; TTY is accurate to ±10% because the angle dominates preload once the bolt is past yield.
Can I reuse TTY bolts?
Generally no. Each TTY cycle stretches the bolt into the plastic region; once stretched, the next cycle uses a different starting length and the angle-based preload spec no longer applies. Most manufacturers say single-use only.
My engine spec says 90° but my torque wrench only goes to 360°. Help.
That's fine — a 90° rotation past snug is a quarter turn. Mark the bolt and the surrounding casting with a marker before you start, and rotate until the marks are 90° apart.
About this tool
What this tool is for: Torque-to-Yield Angle Calculator is a workbench reference for working mechanics, machinists, restoration shops, and serious hobbyists. It is built because the usual online calculators skip the friction loss, the sign convention, the unit conversion, or the engineering code that actually matters on the job.
Purpose and scope
Torque-to-yield tightening angle from yield torque, friction, and rate. Use it only where the OEM specifies TTY — applying TTY to a stretch bolt is wrong.
How to use the body of this page
The sections above this footer — “What this calculator solves,” “Who this is for,” “How to read the results,” and “Limitations” — describe in detail what the formula does, why a tech would use it, how to interpret the number, and where the model is wrong. The FAQ block answers the three or four questions most asked about this specific tool. Together they make up the “About” content for this page; you do not need to look elsewhere.
Known limitations of every MechCalc Pro tool
All calculators on MechCalc Pro run the math in your browser and assume standard conditions (sea-level pressure, ambient temperature, dry friction, textbook geometry). They do not capture manufacturing tolerances, the wear state of your specific parts, environmental extremes, regulatory codes (ASME, DOT, AWS D1.1, etc.), or the load spectrum of your job. They are not a substitute for a stamped engineering review on safety-critical work.
Privacy Policy
No personal data is collected by this calculator. MechCalc Pro does not require an account, an email address, or any sign-up. You open this page, type numbers, read numbers, close the tab. Every calculation runs locally in your browser; we never see the values you enter.
Third-party advertising (Google AdSense)
Pages on MechCalc Pro display ads served by Google AdSense. Google, as a third-party vendor, uses cookies to serve ads based on a user's prior visits to this site or other sites on the Internet. Users may opt out of personalized advertising by visiting Google Ads Settings or the industry-wide page at www.aboutads.info.
Third-party cookies
AdSense and its ad partners may set or read cookies on your browser. These cookies are governed by Google's own privacy policy, not by MechCalc Pro. We do not have access to their contents and we do not share personal data with them because we hold none. We may use a privacy-respecting, IP-anonymized aggregate counter (such as a server log) to see how many people used a tool this month. That counter does not record your inputs, your IP address, or anything that ties a session back to you as an individual.
No sale of personal data
We do not sell, rent, lease, or trade personal information because we hold none. If a future feature ever needs to remember an input (a saved tune-up sheet, for example), that data will live only in your browser's local storage and you will be told before it is written.
Children's privacy
This site is intended for working-age adults using it for work or serious hobby use. It is not directed at children under 13, and we do not knowingly collect any information from children.
Disclaimer
All content on this page, including formulas and calculator outputs, is provided for general informational and educational purposes only. It is not professional engineering advice, it is not a substitute for manufacturer specifications, and it is not a warranty of fitness for any particular purpose.
Mechanical, hydraulic, and welding work can cause serious injury, death, or property damage if performed incorrectly. Numbers produced by this calculator reflect simplified textbook models; they do not capture manufacturing tolerances, material defects, environmental conditions, wear, fatigue, regulatory codes (such as ASME, DOT, or AWS), or the specific service conditions of your job. Always cross-check critical values against the original equipment manufacturer's published specifications and a qualified engineer's review before committing to the job.
By using this site you agree that MechCalc Pro, its author, and its hosting provider are not liable for any loss or damage — direct, indirect, incidental, or consequential — arising from the use of, or the inability to use, the calculators or content presented here. If a calculation is going to inform a safety-critical decision (suspension, brakes, structural welds, pressure vessels, lifting, towing), treat it as a sanity check only.
External links, including Google Ads Settings and AboutAds, are provided for convenience. We don't control their content and we are not responsible for what they say.