The least imposing (and therefore most realistic) Dracula comparison comes from Castlevania III: Dracula's Curse.

Now bear with me, as we have to go through some conversions with some assumptions:

1. Richter is 5'9" (69") or so.

2. Fake Trevor is just as tall as Richter is.

3. Fake Trevor's height is the same as real (CVIII) Trevor's Height.

4. Dracula's 'real' height doesn't truly change between all the games...

Having said that:

-69 / 32 = 2.15625 Inches per Pixel (NES)

Dracula is 49 pixels on his human form when he stands up in CVIII

-49 x 2.15625 = 105.65625 = 8ft, 9.6inches... so 8'9"

Still freakishly tall, but shorter than 10 ft tall.

To put it in perspective, Dracula is now a foot and two inches or so taller than Sagat from Street Fighter 2.