The annual circulation tax (Impuesto sobre vehículos de tracción mecánica) is imposed in Spain on an annual basis based on a Fiscal horsepower. Does anybody know the formula for calculating fiscal horsepower from physical properties of the vehicle?

I am looking for the formula, or algorithm, as opposed to a specific case.

  • This is related to personal finance, how ?? And it pays to be courteous when you want others to help.
    – DumbCoder
    May 19 '16 at 12:21
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    @DumbCoder Assuming the Spanish system is similar to the one I'm used to, fiscal HP will determine the tax costs involved in purchasing/leasing the vehicle so will affect OP's budget. But I'm not sure why you're taking issue with the tone of the post: it seems entirely matter-of-fact.
    – Lilienthal
    May 19 '16 at 12:35
  • 3
    @Grimley - Welcome to Money.SE. Your question proves that there's always something new to learn, if not in our own countries, about how these things are handled elsewhere. I hope someone familiar with this issue will post soon, and help you out. May 20 '16 at 15:40

From the ACEA 2016 Tax Guide, page 250:

a). for four-stroke internal combustion or spark ignition engines:

hp = 0.080 * (0.785 * D^2 * R)^0.6 * N

b). for two-stroke internal combustion or spark ignition engines:

hp = 0.11 * (0.785 * D^2 * R)^0.6 * N


D = the diameter of the cylinder in cm

R = the stroke of the piston in cm

N = the number of cylinders of the engine

c). for rotary engines

hp = Re/7


Re= effective rating

  • that Acea Tax guide looks awesome - I'd been using two other similar books written for fleet managers, and they just didn't go into the detail I need. Thanks @Joe - you have just answered my next 100 questions.
    – Grimley
    May 23 '16 at 9:45

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