The NDS Format Conversion Factor, K_{F}, converts reference design values (allowable stress design values based on normal load duration) to LRFD reference resistances as described in ASTM D5457 Standard Specification for Computing Reference Resistance of Wood-Based Materials and Structural Connections for Load and Resistance Factor Design. The expression for K_{F} is a constant divided by the resistance factor, Φ, and includes the following:
- a conversion factor to adjust an allowable design value to a strength level design value (embedded in the constant),
- a conversion factor to adjust from a 10 year (long-term) load duration to a 10 minute (short-term) load duration basis (embedded in the constant), and
- a conversion factor to adjust for a specified resistance factor, Φ (expressed independently in the denominator)