Foster City's median single-family sale price was $2,562,000 in September 2026, up from $2,050,000 in August. That is a one-month gain of $512,000, about 25%. The September 2026 report from the San Mateo County Association of REALTORS came out October 9, using data compiled by MLSListings, Inc. That headline rests on four sales.
Price per square foot is a better test of whether buyers paid more for the same thing, and it tells a different story. In September 2026 the median single-family home sold for $1,073 per square foot. In August it was $1,048, and in July it was $1,142. Prices didn't jump in September. The homes that sold were bigger. That gap between the headline and the real movement matters most this fall, because the number of homes coming to market has fallen faster than any price line shows.
Four Sales Can Move a Median by Half a Million
A citywide median works when there are dozens of sales behind it. In September 2026, San Mateo city recorded 44 single-family sales and San Mateo County recorded 319. Foster City recorded 4. With four sales, the median is just the midpoint between the second and third prices. Swap one 1,900-square-foot house for one 2,400-square-foot house and the headline can move by six figures without any buyer paying more per foot.
Here is how the summer ran in SAMCAR's single-family city tables:
| Month (2026) | Sales | Median sale price | Median $/sq ft | Avg. home size |
|---|---|---|---|---|
| June | 7 | $2,161,250 | $1,129 | 2,035 sq ft |
| July | 8 | $2,122,500 | $1,142 | 1,870 sq ft |
| August | 11 | $2,050,000 | $1,048 | 2,012 sq ft |
| September | 4 | $2,562,000 | $1,073 | 2,219 sq ft |
July had the highest price per square foot of the four months and the smallest homes. September had the highest median sale price, while its price per square foot was below both June's and July's. Average home size explains most of it. The houses that closed in September averaged 2,219 square feet, compared with 1,870 in July.
In September, the average sale price was $2,428,750, below the $2,562,000 median. With four sales, that can only happen if the cheapest sale sat further below the middle pair than the most expensive sat above it. The spread was lopsided, and the median was set by the two homes in the middle.
The year-over-year view tells the same story. In September 2025, Foster City's single-family median was $2,080,000 on 12 sales, at $1,133 per square foot, with an average home size of 1,975 square feet. Twelve months later the median is about 23% higher. Median price per square foot is about 5% lower.
The Number That Moved for Real Is the Listing Count
Supply changed in September in a way the median doesn't show. Here is the same month a year apart:
| Foster City, single-family | September 2025 | September 2026 |
|---|---|---|
| New listings | 13 | 4 |
| Active inventory | 9 | 3 |
| Sales | 12 | 4 |
| Average % of list price received | 107% | 107% |
New single-family listings fell by roughly two-thirds. Active inventory at the end of September 2026 was three homes in the whole city. SAMCAR put that at 0.4 months of inventory. That was below nearby Burlingame at 0.8, San Mateo at 0.9 and Millbrae at 0.6 in the same table.
Sale-to-list stayed at 107% in both Septembers. SAMCAR reports this as the average percentage of list price received. It is not the share of homes that sold over asking. Buyers paid the same premium over list a year apart, so the drop in sales came from fewer homes being offered, not from weaker demand. Average days on market did rise to 38 in September 2026, from 18 in August and 26 a year earlier. With only four sales, one slow listing can lift that average, so it says little about the market as a whole.
Condos and Townhomes Show the Same Squeeze From the Other Side
SAMCAR groups condos and townhomes into one category it calls Common Interest Development. That segment has enough sales to give a cleaner read, and it points the same way on supply:
- New listings: 24 in September 2025, 15 in September 2026
- Active inventory: 30 in September 2025, 16 in September 2026
- Sales: 10 in both months
- Supply figure in the last column: 3.2 in September 2025, 1.2 in September 2026
SAMCAR labeled that last column "Avg.Mo.toSell" in September 2025 and "Mo. of Inv." in later reports, so the two years aren't a perfect match. The raw inventory count makes the point without that column: 30 active listings a year ago, 16 now, with the same number of sales.
The neighbors have more on offer. San Mateo city ended September 2026 with 85 condo and townhome listings and 3.4 months of inventory. San Mateo County as a whole was at 2.7 months. Foster City's 1.2 is less than half the county figure.
Condo prices have not risen with that scarcity, and this is where the size effect cuts the other way. The Foster City condo median was $1,537,500 in March 2026 and $1,169,000 in September. Some of that drop is size. Units that sold in March averaged 1,602 square feet, and September's averaged 1,348. But price per square foot also fell, from $912 to $796. Year over year the move is smaller, from $817 per square foot in September 2025 to $796 in September 2026. September's condos sold at an average 101% of list price, after an average 35 days on market.
So the two segments are tight in different ways. Single-family homes are scarce and still selling well above list. Condos and townhomes are less plentiful than a year ago but selling close to list, at a slightly lower price per foot.
What Last Winter's Tables Show About the Months Ahead
October 2026 figures will not be published until next month. Last year's tables are the best record of what a Foster City fall and winter looked like. They show last year's pattern and aren't a forecast for this one.
| Month | New single-family listings | New condo/townhome listings |
|---|---|---|
| October 2025 | 7 | 19 |
| November 2025 | 4 | 5 |
| December 2025 | 3 | 2 |
| January 2026 | 5 | 10 |
Last year, new listings in both segments fell sharply in November and December. The single-family homes that did sell in those months went at strong ratios: 108% of list in November 2025 and 109% in December 2025. November had just two single-family sales, with a median of $2,315,000. The condo side went the other way. December 2025 condo sales averaged 96 days on market and 99% of list, with a median of $870,000 on nine sales.
This year matters for one reason. September 2026 is starting from a lower base than September 2025 did. Four new single-family listings is already the level last year didn't reach until November. If the usual seasonal slowdown comes on top of that, the single-family market heading into the holidays could be thinner than last winter's. Each monthly median will then rest on even fewer sales.
Reading the Next Report Without Being Misled by It
For a seller deciding whether to list before the holidays or wait for spring, the useful numbers are new listings and active inventory. A single-family home listed in Foster City this fall faces almost no competing listings within the city. That's a real advantage. The September median is not something to price from. Pricing a 1,900-square-foot home off a $2,562,000 median would mean benchmarking against a month when the homes that sold averaged 2,219 square feet. Price per square foot from recent closings of similar size gives a far steadier anchor.
For a buyer comparing Foster City with San Mateo or Belmont, the September headline makes Foster City look like it got more expensive. At $1,073 per square foot, the city's single-family median sat below San Mateo's $1,305 and Belmont's $1,261 in the same month. What changed in Foster City is how much choice a buyer has. In September 2026 there were three single-family homes to choose from, against 39 in San Mateo city.
For condo and townhome buyers, two things are true at once. Inventory is about half of last year's, and price per square foot is slightly lower. Buyers face fewer options but haven't had to pay more for them.
Frequently Asked Questions
Did Foster City home prices rise 25% in September 2026? No. The single-family median rose from $2,050,000 in August to $2,562,000 in September on four sales. The median price per square foot rose only from $1,048 to $1,073, and it stayed below July's $1,142.
Where does this data come from? Every figure here comes from the San Mateo County Association of REALTORS monthly city reports, compiled from MLSListings, Inc. data. The single-family and condo and townhome tables are published as separate PDFs each month.
Does 107% of list price mean most homes sold over asking? Not necessarily. SAMCAR reports the average percentage of list price received across all sales. A few homes selling well over list can lift that average even if others sold at or below their list prices.
When will October 2026 numbers be available? SAMCAR published September's report on October 9, 2026. October's report should follow on a similar schedule in early November.
If you're deciding whether a Foster City home should list before the holidays or in spring, the answer depends on recent price per square foot for homes like yours, and on how many comparable listings you'd be up against. Those are the numbers Julie Flouty works from when building a pricing plan, and she'll walk you through them for your street before you decide. Let's Connect.
