Blowout Size Calculator 
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The "Blowout size calculator" is an online tool for calculating the blowout size based on the approximation function derived in Kirchschlager & Wolf (submitted, A&A). The blowout size can be calculated as a function of steller temperatue T* and grain porosity P. The grain material is astronomical silicate (Draine 2003) with a bulk density of ρ = 3.5 g cm-3. The optical properties of the grains were calculated with the programm DDSCAT, based on the discrete dipole approximation (Draine & Flatau 1994, 2010). For details see Kirchschlager & Wolf (submitted, A&A).

In the following the two input parameters, T* and P, are shortly described.
The star is considered as a black body with the effective temperature T* .
There is no blowout size for stellar temperatures lower than T* = 5250 K.
Note, that the used approximation equation was derived only for stellar temperatues up to T* = 8200 K.
Porosity is the ratio of the vacuum volume to the total volume of the grain,

 P = Vvacuum / Vtotal = 1 - Vsolid / Vtotal.

It is a dimensionless quantity with values between 0 and 1. A compact sphere is given for P = 0.
Note, that the approximation equation was derived only for grain porosities up to P=0.6.