Cambridge, Massachusetts · FY2026 assessments
Cambridge has 122 acres of surface parking in the middle of a housing crisis
All together, Cambridge's land is worth about $30.6 billion. About 122 acres of surface parking sit on taxable parcels, with about $805 million of land under them, and there are vacant lots on top of that, in a city that badly needs homes. And today's property tax charges you more for putting homes on a piece of land than for leaving it as a parking lot.
I built this site to map that land, to see what a land-weighted property tax would actually do to tax bills here, and to ask whether the land is being valued accurately in the first place.
Full disclosure, I live in a condo here in Cambridge and condos would pay less under the scenarios shown.
- Assessed land, all parcels
- $30.6B
- Taxable land, share of taxable value
- $21.8B · 31%
- Tax-exempt land (universities $5.1B)
- $8.8B
- Surface parking on taxable parcels
- 122 acres
- Land under that parking
- $805M
01 · The problem
Where Cambridge's land is underused
Each shape is a tax parcel, with condo units combined into their building. Start with the Parking and vacant land layer, which shows surface parking along with the 78 taxable parcels of vacant land the Assessor codes as developable (about 29 acres, with $521 million of land). Of the 122 acres of parking on taxable parcels, only 13 are on standalone parking-lot parcels, and the rest sit around shopping centers, labs, offices, and apartment and condo complexes (another 45 acres are on tax-exempt parcels).
Then try Building per $1 of land, which shows how much building sits on each dollar of land. Tax-exempt land like parks and universities is left blank, since a tax change wouldn't reach it. Valuable land with very little building on it is land that could be doing a lot more. Hover over or tap a parcel to see its numbers, and the Tax change layer follows whatever the calculator further down is set to.
Surface parking lots drawn in OpenStreetMap, clipped to Cambridge parcels. Orange lots are on taxable parcels and blue lots are on tax-exempt parcels like universities. Purple-striped parcels are taxable vacant land the Assessor codes as developable or potentially developable (undevelopable land, like private park land, is left out). Volunteers draw the parking map, so some lots may be missing or out of date.
Land value by use
| Use | Land value | Share |
|---|---|---|
| One- to three-family homes | $7.13B | 23.3% |
| Labs and offices | $5.59B | 18.3% |
| Universities (tax-exempt) | $5.14B | 16.8% |
| Government, parks and other tax-exempt | $3.71B | 12.1% |
| Apartment buildings and other residential | $3.43B | 11.2% |
| Condos (land estimated) | $3.27B | 10.7% |
| Shops, hotels, industry and other commercial | $1.73B | 5.7% |
| Parking lots and vacant land | $0.62B | 2.0% |
These are the Assessor's FY2026 land values. Condo units don't carry any land value in the City's open data, so I estimated it from how the Assessor values comparable lots of the same location, size and number of units (see methods). Parking acreage is from OpenStreetMap.
02 · Why it happens
Two lots, two tax bills
Cambridge's property tax uses one rate for land and buildings alike. So when you put homes on a lot, your bill goes up with the value of what you built, and when you leave it as a parking lot, the bill stays low.
The animation below follows two lots on the same street, first under today's rules and then with a building exemption.
Two lots on the same street
Picture two 10,000 sq ft commercial lots on the same street, each with $1.2 million of land. One is a surface parking lot and the other has a $6.8 million building on it. Today the building lot pays about 6.5 times as much tax. If you exempt half of every building's value, the commercial rate goes up to keep the class total the same, so the parking lot's bill goes up by more than half and the building lot's bill goes down.
The same math applies to homes. A parcel pays more when land is a bigger share of its value than the average for its class. In Cambridge, single-family houses have a lot of land per dollar of building and condo buildings have very little, so houses pay more and condos pay less.
03 · The fix
Tax buildings less and land more
Most of a property tax bill is a tax on buildings, and taxing something tends to get you less of it. Land is different. Nobody can make more of it and it can't move away, so taxing it doesn't discourage anything. That's why economists from Adam Smith to Milton Friedman have called a land tax one of the least harmful ways to raise money.
Shifting the tax from buildings to land does a few things.
- It rewards building and fixing up. A new home, an addition or a renovation adds less to the tax bill.
- It makes holding land idle more expensive. A surface parking lot or a vacant lot pays closer to what a full building on the same land would pay, so there's more reason to put it to use.
- It gives back value the public created. Land in Cambridge is valuable mostly because of what's around it, like the Red Line, jobs, schools and zoning. A land tax returns part of that to the public, and owners keep the value of what they build.
- It's hard to dodge. Land can't be hidden or moved, and Cambridge already assesses land and buildings separately every year.
You don't have to go all the way to a pure land tax. Related policies include a two-rate tax (land taxed at a higher rate than buildings, as Pittsburgh did from 1913 to 2001), the building exemption modeled on this site, tax breaks for new housing like the Urban Center Housing TIF, and fees on vacant land or surface parking.
The evidence is real but modest. Studies of Pennsylvania's two-rate cities find somewhat more construction, and Cambridge would likely see something similar. Here a 50% building exemption cuts the tax on buildings from 0.67% to 0.50% of value, which is worth about 3% of the cost of a new building, so it shifts tax between groups more than it changes what gets built. The next section shows who would pay more and who would pay less.
Cambridge can't do this on its own, though. The state constitution keeps the power to tax with the state, so it would take a state law (see section 05).
04 · What it would mean
Who would pay more, and who would pay less?
Pick how much of every building's value to exempt. Each tax class still raises exactly what it raised in FY2026, so the rate goes up as the building exemption grows. Owner-occupants keep the residential exemption, recalculated on the new values, which keeps each owner-occupant's savings close to today's $3,400. All 25,400 taxable properties get recomputed right in your browser.
At a 50% building exemption, the median owner-occupied single-family home pays 12% more (about $930 a year), and the median condo pays 14% less. So in Cambridge, a land value tax would mostly move tax off condos and onto houses, and it wouldn't cut the typical homeowner's bill.
Idle land pays the most. Parking lots pay about 58% more, commercial vacant land about 59% more and residential vacant land about 49% more.
The reason is that condo buildings pack the most value onto each square foot of land, so land is only about 20% of a condo's assessed value, compared with 41 to 46% for every other housing type, apartment buildings included. So two-families pay about 11% more and apartment buildings with 4 or more units about 9% more.
A gentler version, a 20% building exemption plus a 35% residential exemption, leaves owner-occupied single-family homes about even (0.8% less), while rental property pays about 5% more. You can try both settings below.
About the 35% option. A bigger residential exemption gives every owner-occupant a bigger deduction, and rental and investor property pays for it. So any homeowner gain in this setting comes from the bigger exemption. The land/building change by itself still moves tax off condos and onto owner-occupied houses.
Commercial property included. Labs, which have expensive buildings on their land, pay less. Small shops, restaurants and parking lots pay more. That's why I'd recommend residential-only coverage when Cambridge opts in.
| Group | Properties | Median change | Median $/yr | Share paying more |
|---|
A few notes on the groups. "Owner-occupied" means the property has the residential exemption in the City's open data, which misses about 900 owner-occupants. The two- and three-family and condo rows include both owner-occupied and rental properties, and parking lots and vacant land include both classes. Condo land is estimated. Values are held at FY2026 levels, and a real reform would phase in over several years.
Condos, two- and three-families, and apartments: what's the difference?
These groups are about who owns a building and how it's taxed, not what it looks like. The same triple-decker can be a three-family or three condos, depending on how it's owned.
- Single-, two- and three-family homes. One owner, one parcel and one tax bill, with land and building valued separately. Often the owner lives in one unit and rents out the others.
- Apartment buildings (4 to 8 units, and 9 or more). Also one owner and one tax bill, usually a landlord renting every unit.
- Condos. Each unit is owned separately and gets its own tax bill. The owners share the land and common areas, each with a percentage interest set in the building's master deed under state condo law (Chapter 183A). The City's open data puts $0 of land value on the units and records the lot on a separate building record, so I estimated each building's land and split it among its units by value.
The residential exemption works differently too. Every owner-occupied condo unit gets its own exemption (worth about $3,400 a year), while an owner-occupied three-family gets one for the whole building, and its rented units get none.
Why is the same building worth more as condos?
Selling homes one at a time to people who'll live in them usually brings in more than selling the whole building to someone who'll rent it out.
- An investor pays for the rent. Someone buying a three-family or an apartment building to rent out works out what the rents will bring in after costs, and pays a price that earns a return on that, so rent levels cap the price.
- A homebuyer pays for a home. Owning comes with things a landlord doesn't get on rented units: mortgages designed for homebuyers, no tax on most of the gain when you sell your home, and Cambridge's residential exemption for every owner-occupied unit.
- More buyers, smaller pieces. Far more people can afford one $800,000 unit than a $2.4 million building, and more buyers push prices up.
- Conversions usually come with renovation. New kitchens, bathrooms and systems add real building value.
On average the Assessor values small condo buildings at about 25% more per square foot of living space than comparable two- and three-families in the same area. What the data can't tell us is how much of that extra value belongs to the land and how much to the building. My estimate puts it in the building, which is a big part of why condos pay less in these scenarios. If all of it were land, condos would still pay less at a 50% building exemption, but about 9% less instead of 14%. That's one reason I'm asking Assessing to publish condo land values.
05 · How Cambridge gets there
Start with the land values
There are two parts to getting there. Cambridge can start on the first one now, since getting land values right doesn't take a new law, and it matters even more under any land-weighted tax. The second part needs the state.
Questions for the Assessing Department
I'm asking these as questions, since each one points to a pattern in public data that Assessing may well be able to explain. I'd hold off on dollar effects until the Department answers and the state Division of Local Services confirms the math.
- Commercial and residential land schedules. When I compare parcels of the same size, tax district and zoning, commercial and industrial land is assessed about 37% lower per square foot than residential land (95% interval 29% to 43% lower). What explains the difference, and which land schedules apply to each class? Consistent across tests
- Parking and vacant land. Land classed as parking lots is assessed 27% to 50% below other commercial land of the same size nearby, depending on how I set up the comparison (the intervals run from 10% to 70% below). Would Assessing review parking and vacant parcels against comparable land? Fragile result
- Surface parking on other parcels. OpenStreetMap shows 122 acres of surface parking on taxable parcels, and only 13 of those acres are on parcels classed as parking lots. Most of it belongs to shopping centers, offices and labs. How does the land schedule treat big surface lots attached to other uses? Map data, volunteer-drawn
- Condo land. Condo units show $0 land value in the open data. Could Assessing publish each condo building's land value, and each unit's share of it by percentage interest? My estimate checks out well against the land the Assessor carried on lots before they were converted to condos (typically within 4%), but for large buildings it's an extrapolation (typically within about 20%). Data gap
Why the answers matter to residents
Under FY2026 rules, correcting commercial land values would only move tax around within the commercial class. But the City projects that starting in FY2028, commercial property will pay the legal maximum (175% of its share of total value). If that happens, a real gap in commercial land values would matter to residents, since correcting the full gap could lower the residential levy by up to about $38 million a year. Fixing parking lots alone would move less than $1 million. Upper bound, pending state confirmation
05 · The state's part
What a state law could do
The legal limits
Cambridge can't adopt a land value tax on its own. The state constitution lets the Legislature tax property by use class, but it requires equal treatment inside each class:
“…the general court may classify real property according to its use in no more than four classes and to assess, rate and tax such property differently in the classes so established, but proportionately in the same class, and except that reasonable exemptions may be granted.”Mass. Const. Amend. Art. 112
The Home Rule Amendment keeps the taxing power with the state:
“Nothing in this article shall be deemed to grant to any city or town the power to … levy, assess and collect taxes”Mass. Const. Amend. Art. 89, §7
All four use classes are already taken, so land and buildings can't become separate classes. That leaves the “reasonable exemptions” clause, meaning a law that exempts part of every building's value. No court has tested that, and my best guess is a 25% to 40% chance it would survive review by the Supreme Judicial Court, but I'm not a lawyer.
Two asks for the Legislature
1. Expand the Urban Center Housing TIF (c.40 §60). Cities can already exempt the added value of new housing for up to 20 years, but only inside approved commercial-center zones, one project at a time, and only if at least 15% of the units are affordable at 80% of area median income (or 25% at 110%). A bill could let cities offer standard, by-right exemptions for new housing across more of the city. Since it builds on an existing statute, it's on the firmest legal footing. Exemptions tied to construction dates have their own fairness problems, though, so I'd keep the bill close to the TIF structure.
2. A local-option building exemption. Any city could choose to exempt a share of building value, with these safeguards:
- the city chooses which classes it covers;
- class shares of the levy are set on values before the exemption, so commercial owners cannot shift tax onto residents;
- the residential exemption is recalculated in proportion;
- single-rate towns may pool all classes;
- a phase-in and a hardship deferral.
The case for it is density and fairness. In the four other cities I modeled, idle land pays more and two- and three-families, condos and apartments pay less. In Cambridge a 50% exemption would raise the typical single-family bill, so I'd want Cambridge to go first with the gentler version described above.
Cambridge first, in this order
- The Legislature passes the local-option building exemption.
- The legal question gets settled, ideally with an advisory opinion from the Supreme Judicial Court (the state's highest court).
- Assessing publishes condo land values.
- Cambridge votes on the gentler version (residential only, a 20% building exemption with a 35% residential exemption, phased in).
06 · Elsewhere in Massachusetts
Other Massachusetts cities
I ran the same 50% building exemption on Worcester, Springfield, Fitchburg and Leominster using state parcel data. In every city, vacant and parking land pays 59% to 72% more, and two- and three-family homes, condos and apartments pay less. The median single-family home pays 0% to 4% more (about $0 to $245 a year). I didn't find a Massachusetts city where the median single-family homeowner pays less.
That's because in Massachusetts cities, single-family homes have the highest land share of value in the residential class, and vacant and parking land is too small a share of the tax base to pay for a cut for homeowners.
For Cambridge I used the residential exemption roll to find owner-occupants, and for the other cities a mailing-address match. Condo land is estimated everywhere, from lot size and comparable nearby lots; Leominster's large condo complexes are the least certain. I assumed residential exemptions are zero outside Cambridge (I haven't verified that for Worcester or Springfield). The "pooled" rows tax all classes at one rate, which is only an option for single-rate towns.