Fracture Toughness Converter: MPa√m to ksi√in
Convert fracture toughness (KIC) between MPa√m (SI) and ksi√in (US). Whether you need MPa√m to ksi√in or ksi√in to MPa√m, this converter uses the exact factor 1 ksi√in ≈ 1.09884 MPa√m. Essential for fatigue and fracture mechanics, aerospace, and failure analysis. Free, runs in your browser—no sign-up required.
What is fracture toughness?
Fracture toughness (KIC) is the stress-intensity factor at which a crack propagates under mode I (tensile) loading. Its dimension is stress × √length, so units are MPa√m (SI) or ksi√in (US). It characterizes resistance to crack growth and is used in damage tolerance and failure analysis. This converter supports both units and uses MPa√m as the base; 1 ksi√in = 6.89476 × √0.0254 MPa√m ≈ 1.09884 MPa√m.
How fracture toughness conversion works
The dimension of KIC is [stress] × [length]1/2. In SI: MPa × √m = MPa√m. In US: ksi × √in = ksi√in. Since 1 ksi = 6.89476 MPa and 1 √in = √0.0254 √m, we have 1 ksi√in = 6.89476 × √0.0254 MPa√m ≈ 1.09884 MPa√m. Convert your value to MPa√m using the source factor, then divide by the target factor. Example: 50 ksi√in → 50 × 1.09884 ≈ 54.94 MPa√m.
Key fracture toughness units explained
Only two units are in common use for KIC; both are supported.
Megapascal root meter (MPa√m)
Factor: 1 (SI base unit)
The SI unit for stress-intensity factor. Used in ISO, European standards, and most international fracture mechanics.
Kilopound per sq in root inch (ksi√in)
Factor: 1 ksi√in ≈ 1.09884 MPa√m
US customary unit. Common in ASTM (e.g. E399, E1820) and aerospace. 1 ksi = 1000 psi.
When to use MPa√m vs ksi√in
MPa√m is the SI unit and is used in ISO and most international standards (e.g. ISO 12135). ksi√in is common in US ASTM (E399, E1820) and aerospace specs. Use this converter to match test reports, material datasheets, and design codes when units differ.
Who uses a fracture toughness converter?
Structural and materials engineers convert between MPa√m and ksi√in when comparing specs or test data from different regions. Aerospace and defense often cite KIC in ksi√in; European sources use MPa√m. Failure analysts and labs need to report or compare values in both units. Students and educators use it for fracture mechanics courses. All conversions run in your browser—no data is sent to a server.
Common fracture toughness conversions at a glance
Handy reference for MPa√m to ksi√in and back.
| From | To | Formula | Example |
|---|---|---|---|
| MPa√m | ksi√in | ÷ 1.09884 | 55 MPa√m ≈ 50 ksi√in |
| ksi√in | MPa√m | × 1.09884 | 50 ksi√in ≈ 54.94 MPa√m |
Why MPa√m is the SI unit
Stress-intensity factor K has dimension [stress] × [length]1/2. In SI, stress is Pa (N/m²) and length is m, so K is Pa√m. MPa√m (10⁶ Pa√m) is the practical unit. ksi√in is the US analogue: 1 ksi√in = 6.89476 × 10⁶ Pa × √(0.0254 m) ≈ 1.09884 MPa√m. This converter uses that exact factor.
Avoiding common mistakes
Don't confuse fracture toughness KIC (MPa√m or ksi√in) with toughness (energy per volume, e.g. J/m³)—they have different dimensions. Don't use a simple psi-to-MPa factor without the √length: 1 ksi√in ≠ 6.895 MPa√m (you must include √0.0254 for the inch-to-meter conversion). Always state the unit when reporting KIC. This converter uses the correct dimensional factor for both units.
Fracture Toughness Conversion FAQ
? How do I convert MPa√m to ksi√in?
Divide MPa√m by 1.09884 to get ksi√in. So 55 MPa√m ≈ 50 ksi√in. To convert ksi√in to MPa√m, multiply by 1.09884.
? What is the SI unit for fracture toughness?
The megapascal root meter (MPa√m). Fracture toughness (stress-intensity factor) has dimension stress × √length, so in SI the coherent unit is Pa√m; MPa√m is the practical unit. This converter uses MPa√m as the base.
? Why is the conversion factor 1.09884 and not 6.895?
6.895 is the psi-to-MPa factor for stress only. Fracture toughness has stress × √length, so we need 1 ksi√in = (6.89476 MPa) × (√0.0254 √m) ≈ 1.09884 MPa√m. The √0.0254 comes from converting √in to √m.
? Where is fracture toughness used?
Fracture toughness KIC is used in damage tolerance analysis, fatigue and fracture mechanics, aerospace (e.g. NAS, MIL-HDBK), and failure investigation. It defines the critical stress-intensity factor for crack growth under mode I loading.
? Is ksi√in the same as psi√in?
No. 1 ksi√in = 1000 psi√in (since 1 ksi = 1000 psi). So 50 ksi√in = 50,000 psi√in. When a US spec says "ksi√in" or "ksi-in^0.5" it means kilopound per square inch root inch.
? How do I convert ksi√in to MPa√m?
Multiply ksi√in by 1.09884 to get MPa√m. So 50 ksi√in ≈ 54.94 MPa√m. The factor is 6.89476 × √0.0254 ≈ 1.09884. To convert MPa√m to ksi√in, divide by 1.09884.