The blocks vary depending on what part of town you're in. Assuming you don't have access to plat surveys at a public library, Google Earth may be your best option.

Most cities/county tax assessors offices offer online access to plat maps.

Thanks Living in Gin.

I would think they are 660' x 660'
Given there are 8 blocks in a 5,280' Mile.

The blocks in the Loop are roughly 400' X 400', or slightly less.

Out in the neighborhoods, each half-mile square on the street grid is usually divided into four blocks in one direction and eight blocks in the other. That would give you a standard 660' X 330' block, minus the width of the streets.

See the link above if you're looking for actual dimensions of a specific property.

For NYC (Manhattan north of Houston Street, specifically):

East-West streets are spaced every 200', and the streets themselves are 50 or 60 feet wide. Roughly every half-mile, an east-west street is 100 feet wide (example: 42nd Street). Thus, the "short blocks" are 140-150 feet long.

The avenues that run north-south are usually 100 feet wide, but their spacing is more irregular. IIRC, the "long blocks" range from 400-600 feet in length.

Trivia fact: Lexington Avenue was not part of the original city grid, but was later inserted between Third and Fourth (later renamed Madison) Avenues to enchance access to Grammercy Square and boost property values.

Not sure about New York, but in Chicago, a block is a block - 100 Units. There are 800 units in a mile, in both directions. The mid-block quaternary streets are not actualy blocks in terms, albeit a description that works.."on the same block, next block over", etc. A block is a set unit of measurment with which you navigate the city. Chicago Avenue is 4 Blocks south of Division regardless of the fact that there are 9 Different streets between. Belmont (3200) is 4 miles north of madison (0 N/S), as it is 32 blocks north. That's my useless bit of info for the day.

All I know about blocks I learned walking to and from school in Chicago, over the snow drifts that were 12' high at times, barefoot of course. Each block was seemingly a mile long. It still haunts me.

However, walking in Manhattan, now shod in expensive boots, I became sure that each block was in fact 3 miles long. It didn't help that I had to stumble around the massive trash heaps in front of residences that surely cost upwards of $6M or more. Maybe it was all the leaping over those debris piles that made NYC "blocks" seem far longer than their Chicago counterparts.

[yet another attempt by a 2nd City-er intended to demonstrate the superiority of Chicago over NYC]

*bump*

my google search for 'city block size' pulled up this thread.... yeay archinect!

surprisingly there are no lists or comparisons between different cities in my graphic standards or in wikipedia...

I'm trying to figure out how big to make the blocks for a senior village in the highlands of vietnam- I want them to be walkable. 500' seems to be a good maximum length in one direction, while 400' is more friendly. of course the smaller the blocks, the more pavement i'm designing... I'll just add more trees to compensate for the higher impervious cover.

Adding more trees, trekiller? interesting...

somewhere out there is a web page with the light rail lines of many major cities at the same scale as one another - I'm swamped or I'd google it. I'd be less swamped if I went back to work though. bye...

Addendum (for plots not blocks):

In 1811 New York City implemented its now-famous gridplan, which was laid out in a north-south direction and the narrower streets in an east-west direction. In addition lot sizes were standardized at 25 feet wide by 100 feet deep, a size seen as adequate for early 19th century homes and businesses (Spann, 1988)