Why is a Piece of a Proscar Pill Smaller Than a Propecia Pill?

I know this may seem like a really insignificant question, but it’s been a looming one none the less:

If you cut a 5mg finasteride into 4 equal pieces you would have 1.25 mg of finasteride correct? Why, then, is a 1/4 size of 5mg smaller than a 1mg Propecia pill? Especially taking into consideration theres more finasteride in a 1/4 piece.

Thanks for taking a moment to answer such a ridiculous question.

Pills have fillers and the drug companies determine how to make it and what type of fillers there are. These fillers are called excipients (see Wikipedia, and basically make it easier for consumers to handle the pill.

From what I’ve read, the excipients in Propecia are: lactose monohydrate 110.4 mg, microcrystalline cellulose, pregelatinized starch, sodium starch glycolate, docusate sodium, magnesium stearate, talc, hypromellose, hydroxypropyl cellulose, titanium dioxide (color E171), yellow and red ferric oxide (color E172).