If my realtor agreed to a 4% total commission, how much more should I estimate for other closing costs?

Budget roughly another 1 to 1.5% of the sale price on top of the commission, then replace the estimate with a real net sheet. In California, that bucket covers title and escrow fees plus whatever buyer-requested items land in the purchase agreement: a termite or pest inspection, a home warranty, a natural hazard disclosure (NHD) report, and similar line items. The mix shifts with what the buyer negotiates, and it varies meaningfully by state and market. Because those costs move around, ask your agent for a formal estimated closing statement, sometimes called a net sheet. A good agent provides one as a matter of course. Our own practice is to estimate on the conservative, higher-cost side, assuming the termite charge and the home-warranty request, so that if those items never materialize you net more than projected instead of getting a surprise at closing. One more note: all of these figures, the commission included, are negotiable and regional. Treat the 1 to 1.5% as a planning number, and let the itemized net sheet for your actual property and contract be the bottom line.