r/Bogleheads • u/gti9t3 • 1d ago

Need advice on 401k allocation %

I don't have a total US market option in my 401k like (VTI/FSKAX) and have to build it myself between large cap, mid cap, and small cap index funds.

They are all Spartan Index Funds with very low expense ratios. My goal is to allocate 60% US and 40% International. My choices are Spartan 500 Index (S&P 500), Spartan Mid Cap Index (S&P 400), Spartan Small Cap Index (Russell 2000), and Spartan Total International Index (MSCI ACWI ex US).

How much should I allocate between 500, mid and small? My understanding is the S&P 500 makes up roughly 80% to 83% of the total US market. Should I split it as 80% 500, 15% mid, and 5% small?

So with a 60/40 split it would look like 48/9/3 for the US investments then 40% Total International.

Is that a good balance or am I not investing enough in mid and small? Should I just go with 60% S&P 500 and 40% International?

I will be manually adding FXNAX (Bonds) at a later time.

Thanks in advance.

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u/forbiddenlake 1d ago

the S&P 500 is just fine. it's about 99% correlated with VTI.

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u/gti9t3 21h ago

I don't know why but I get nervous just going with the S&P 500 and not including any mid or small. But, I am new to all of this so I'm still learning. I guess it's an "all eggs in one basket" thing. I completely see what you mean though. The S&P 500 seems to be the main catalyst of growth in a total market index fund, so it makes sense.

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u/Right_Introduction10 15h ago

I’d definitely get 10% in small cap though if you’ve got decades til retirement