Diameter or Circumference? How Each Bay Area City Measures a Tree
The single most common permit mistake is measuring the wrong thing at the wrong height. Each city's unit, height and multi-trunk rule, with a converter.
Dataset version 2026-10-09 · 35 cities · by Michael Schuck, ISA Certified Arborist WE-15750A, Urban Forest Professional WE-15750AF
Most cities measure at 54 inches above grade, but Berkeley, Campbell, Los Altos and Woodside measure at 48 inches, Tiburon at 24 inches, and Redwood City at the widest point between 6 and 36 inches. Fourteen cities write their thresholds in circumference. A 12-inch-diameter trunk is about 38 inches around; a 12-inch-circumference trunk is under 4 inches across.
Circumference to diameter
Wrap a tape around the trunk at the height your city specifies. Circumference divided by 3.14 is diameter.
| City | Measures | Height above grade | Threshold as written | Multi-trunk rule |
|---|---|---|---|---|
| Atherton | Diameter (DBH) | 54″ | 48" circumference (15.2" dia) at 54" above natural grade | No codified multi-trunk aggregation in 8.10.020(L) |
| Belmont | Diameter (DBH) | 54″ | 10" DBH (natives) / 14" DBH (others), at 4.5 ft above natural grade | Up to three largest secondary stems totaling 10" (natives) / 18" (others) |
| Berkeley | Circumference | 48″ | 18" circumference single / 26" aggregate, at 4 FEET (48") above ground | Multi-stem: 26" aggregate circumference |
| Burlingame | Diameter (DBH) | 54″ | 44" circumference (14" dia) at 54" (DSH) | Per 11.06 definitions (DSH standard) |
| Campbell | Diameter (DBH) | 48″ | 12" diameter (38" circumference) at FOUR FEET (48") above adjacent grade | At least one trunk >=12" dia (21.32.050(B)) |
| Cupertino | Diameter (DBH) | 54″ | Specimen: 12" dia single trunk (38" circ) / 24" aggregate multi-trunk (75" circ), at 4.5 ft | Multi-trunk DBH inclusive of ALL trunks, straight sum, threshold 24" (14.18.020) |
| Danville | Diameter (DBH) | 54″ | 10" dia single (natives) / 36" heritage, at 4.5 ft above natural grade | Natives: 20" combined multi-trunk; heritage limited to single-trunk trees (multi-trunk cannot be heritage) |
| Foster City | No private threshold | N/A, no private threshold exists | N/A | |
| Fremont | Diameter (DBH) | 54″ | 10" DBH (natives) / 18" DBH (any species) / 6" DBH (vacant, underdeveloped or development lots), at 4.5 ft | Per DBH definition (18.215.030) |
| Hayward | Diameter (DBH) | 54″ | 4" DSH (natives) / 8" DSH (non-natives, commercial property or residential front yards only) / 36" DSH (redwoods), diameter at 54" | Largest three trunks combined (B2-0) |
| Hillsborough | Diameter (DBH) | 54″ | 18" cumulative diameter at 4'6" (54") above natural grade | CUMULATIVE diameter, multiple trunks added together |
| Lafayette | Diameter (DBH) | 54″ | 12" DSH developed natives / 6" undeveloped natives / 6" riparian, at 4.5 ft | Riparian: any component trunk 4"+ protected |
| Los Altos | Diameter (DBH) | 48″ | 12" dia general / 10" natives, at 48" (FOUR FEET) above grade, deviates from 54" standard | Per DBH definition |
| Los Gatos | Diameter (DBH) | 54″ | 12"/8"/4" diameter tiers at 4.5 ft | 18" sum of trunk diameters (developed residential) |
| Menlo Park | Circumference | 54″ | 47.1" circ (15") / oaks 31.4" circ (10"), at 54" above natural grade | Measure diameter below main union; if union below grade, each stem = standalone tree; multi-trunk under 12 ft tall excluded (13.24.020) |
| Mill Valley | Circumference | 54″ | Heritage: 65-95" circumference by species, at 4.5 ft | Per circumference definitions |
| Milpitas | Circumference | 54″ | 56"/37" circumference at 4.5 ft (taut tape) | Any trunk meeting circumference (X-2-7.01) |
| Mountain View | Circumference | 54″ | 12" circ (heritage 3 genera) / 48" circ (all species), at 54" above natural grade | Per circumference standard |
| Oakland | Diameter (DBH) | 54″ | 4" DBH (CLO) / 9" DBH (others), at 4.5 ft | Per DBH definition |
| Orinda | Diameter (DBH) | 54″ | 12" (oaks, developed) / 6" (any, vacant/downtown) / 4" (riparian), at 4.5 ft | Riparian: combined cross-sectional area equal to single 4" stem |
| Palo Alto | Diameter (DBH) | 54″ | 11.5" / 15" / 18" DBH at 54" above natural grade | Per Tree Technical Manual |
| Piedmont | No private threshold | N/A, no private threshold | N/A | |
| Pleasant Hill | Diameter (DBH) | 54″ | 9" (natives) / 18" (non-natives), diameter at 54" (DBH) | Per DBH definition |
| Redwood City | Circumference | measured at widest point between 6" and 36" above ground | 38" circumference measured at WIDEST point between 6" and 36" above ground | Single trunk standard (Sec. 35.1) |
| San Carlos | Diameter (DBH) | 54″ | 9"/11"/15" dia (heritage) / 11" (significant), at 54" | Per code definitions |
| San Francisco | Diameter (DBH) | 54″ | >12" DBH / >20 ft height / >15 ft canopy (independent prongs), DBH at 4.5 ft (BUF) | Per DBH (BUF guidance) |
| San Jose | Circumference | 54″ | 38" circumference at 54" above natural grade | Multi-trunk: sum of trunk circumferences (13.32.020.L) |
| San Mateo | Diameter (DBH) | 54″ | 10" (oaks) / 15" (others) dia at 54" above natural grade | Per Administrative Guidelines |
| San Rafael | No private threshold | N/A, no private threshold | N/A | |
| Santa Clara | Diameter (DBH) | 54″ | 12" dia (specimen) / 38" dia (any species), at 54" above grade; multibranched: 38" below first fork | Multibranched: >=38" below the first fork |
| Saratoga | Diameter (DBH) | 54″ | 6" (natives) / 10" (others) DBH at 4.5 ft | Multi-trunk DBH = largest trunk + 50% of diameter of each additional trunk (15-50.020(g)) |
| Sunnyvale | Circumference | 54″ | 38" circumference at 4.5 ft (54") above ground | Any one trunk >=38" circ, OR all trunks totaling >=113" circ (19.94.030) |
| Tiburon | Circumference | 24″ | 60" circumference at 24" above ground (heritage); oaks any size | Per trunk circumference |
| Walnut Creek | Circumference | 54″ | 28" circ single / 40" aggregate multi-stem, at 4.5 ft above natural grade | 40" aggregate circumference multi-stem |
| Woodside | Circumference | 48″ | 24"/30"/36" circumference at 48 INCHES above mean natural grade | Madrone/blue oak/buckeye: SUM of all trunk circumferences at 48"; CA bay laurel: largest trunk only |
Measuring correctly
- Find the height your city uses and mark it on the trunk with a tape from the ground on the uphill side.
- Wrap a flexible tape around the trunk at that mark, snug but not tight. That is circumference.
- Divide by 3.14 for diameter. Cities that say DBH, DSH or "diameter" want that number.
- Multi-trunk trees: apply the city's rule in the table. Some add trunks, some take the largest, some measure below the first fork.
Questions
Why do cities use different heights?
Older ordinances adopted 48 inches; the ISA standard is 54 inches (4.5 ft); a few towns wrote their own. The code governs, not the standard.
Which number goes on the application?
The one the code names, in the unit the code uses. If the form asks for diameter and the code is written in circumference, give both and say how you measured.
Every cell comes from the verified 35-city dataset (CSV and JSON available there). Each city page links the code section and source.
Borderline measurement?
A city arborist or a consulting arborist measuring to the code's standard settles it before anyone cuts.