700c wheels are 622mm diameter, same as 29".
From Sheldon Brown's site:
Fractional sizes:
Fractional ISO Applications
36 inch 787 mm Unicycles, some novelty bicycles
32 inch 686 mm Unicycles, some novelty bicycles
29 inch 622 mm This is a marketing term for wide 622 mm ("700C") tires.
28 x 1 1/2 635 mm English, Dutch, Chinese, Indian Rod-brake
roadsters
(Also marked F10, F25, 700 B)
622 mm (F.13) Rare Canadian designation
28 x 1 5/8 x
1 1/4 Northern European designation for the 622 mm (700 C) size
27 x anything except "27 five" and 609 mm Dutch 630 mm Older
road bikes.
27 x 1 1/2 609 mm Rare Dutch size
26 x 1 (650 C)
571 mm Triathlon, time trial, small road bikes. Old Schwinn S-4
26 x 1 1/4 597 mm Older British sport &
club bikes
26 x 1 3/8
(S-6)
Schwinn "
lightweights"
26 x 1 3/8 (E.A.3) 590 mm Most English
3-speeds, department-store or juvenile 10 speeds
26 x 1 1/2 (650B) 584 mm
French utility, tandem and loaded-touring bikes,
a very few Raleigh (U.S.) & Schwinn mountain bikes.
26 x 1 3/4
(S-7) 571 mm
Schwinn cruisers
26 x 1, 1 1/8 High performance wheels for smaller riders, common on Cannondale bicycles
24 x 1 520 mm High performance wheels for smaller riders;
Terry front
24 x 1 1/8 520 mm or
540 mm!
Caveat emptor
24 x 1 1/4 547 mm British or Schwinn Juvenile
24 x 1 3/8
(S-5)
Schwinn Juvenile
lightweights
24 x 1 3/8
(E-5) 540 mm British Juvenile, most wheelchairs; common on women's utility bicycles in Japan.
20 x 1 1/8
20 x 1 1/4
20 x 1 3/8 451 mm Juvenile
lightweights,
BMX for light riders, some recumbents, some folding bicycles
20 x 1 3/4 419 mm
Schwinn juvenile
18 x 1 3/8 400 mm British juvenile
17 x 1 1/4 369 mm Alex
Moulton AM series
16 x 1 3/8 349 mm Older Moulton; Brompton & other folders, recumbent front, juvenile
16 x 1 3/8 337 mm Mystery tire
16 x 1 3/8 335 mm Polish juvenile
16 x 1 3/4 317 mm
Schwinn Juvenile
12 1/2 x anything 203 mm Juvenile, scooters
10 x 2 152 mm Wheelchair caster
8 x 1 1/4 137 mm Wheelchair caster
