The Magical Probability Calculator calculates magically modified probability per Peter J. Carroll's equations of magic in *The Octavo*, *The Apophenion*, and *Liber Kaos*. The calculation requires five parameters in the range of 0 to 1 (numbers outside the range are constrained to 0 or 1) for **natural probability**, **gnosis**, **link**, **subliminalization**, and **belief**, respectively. The pertinent equations are:

**Magic:**Ψ = G * L * S * B

**Spell:**P_{Ψ}= P + (1 − P)Ψ^{1/P}

**Antispell:**P_{Ψ}= P − PΨ^{1/(1 − P)}

I have made two earlier versions of this calculator with Processing (1, 2); one with Python; and one with Scratch. I have also made an electronic device that demonstrates these relationships analogically: the TKS-127 Magical Probability Computer.