You probably will have trouble for your purposes improving on this

• Sekonic EV - Lux inter-conversion table

"Close enough"*

• Lux = 2.5 x 2^EV

• EV = log_2(Lux/2.5)

ie 2 raised to the power of the EV value and multiplied by a constant.

*_The above Seconic table best fits about Lux = 2.502442 x 2^EV

2.5 will be fine enough for mere mortals.

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A bit of Googling turned up this Stack Exchange question & answers from 2011 - I need not have bothered :-)

Wikipedia's Exposure value entry is well worth reading. I got that link from the prior Q&A!. Note that the value of 2.5 or 2.502442 or ... is a compromise one and relates, among other things, to the flatness of the subject and the degree to which light is reflected off it back towards the source and also to the sensor shape (eg flat (with cosine response ie effective incident light is the normal component which is proportional to the cos of the incident angle) or hemispherical with cardioid response (you don't really expect me to try and explain that, do you ? :-) ) . [It almost makes sense on inspection].

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Notes:

Lux = k x log(EV)

Lumens = Lux x Area_illuminated or, more usually,

Lux = lumens per area

A light level of 1 EV requires 1 second exposure at 1/100 th second at f/1 with 100 ISO sensor sensitivity.