“Have twice the” question

This is how I say it:

“You have twice the experience I have”

to me it feels right, but searching examples on the net, I don’t quite find a similar example. I could rephrase. I think these are safe:

“You have twice more experience than I have” or “You have twice as much experience as I do”

but back to my original way of saying it, is there something missing before “I have”?

“You have twice the experience that I have”

It sounds better without the “that” to me.

Solution 1:

You're saying it fine.

Twice is one of several adverbs that can be followed by a noun phrase describing a quantity to further modify that quantity. (With rephrasing, you could use numbers too!) The Oxford English Dictionary explains this form in 2a. for "twice, adv. (n. and adj.)":

a. with a numeral, or a noun or noun phrase expressing quantity: Two times as much as; double of.

Compare several alternative insertions where the syntax is otherwise unchanged:

You have double the experience I have.

You have half the experience I have.

You have ten times the experience I have.

And consider similar insertions for the object following it.

You have twice the ketchup I have.

You have twice the money I have.

You have twice the number of fans I have.

Solution 2:

Twice means 2x. Twice more means thrice or 3x.

To say that someone has two times the experience you do, as @Jim commented, it's most common to use:

You have twice the experience I have.

There are other ways, but people often misunderstand percentages, so the simplest method is recommended.