From reading here, most builders have settled on wheel diameter and top speed desired when they begin pondering motor Kv selection, voltage to be used, and gear-down options. I have compiled this chart to make the process a little easier.

This link is a pedal cadence calculator (thanks, Drunkskunk), but if the sprocket and chainring tooth-count numbers entered are the same (1:1) then the pedal-cadence will be the same as the rear-wheel rpm.

http://www.machars.net/bikecalc.htm

If you want to use a tire with an odd outside diameter (such as a fat moped tire on a 20-inch bicycle wheel, which would typically be 22-inches), you go to the tire selection and click on “other", then enter a number of the tire outside diameter into the next square in inches (decimals allowed, 1/4-inch is 0.25).

For instance, if using a custom tire with an outside diameter of 60-centimeters, you would use an online conversion calculator, then enter the result of 23.62 (inches) into the cadence calculator

__Other--->__wheel (using 1:1 gears) to find the top-speed/rpm result. Suggestions welcome...

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Here's another method:

(10 mph x 5280 feet/mile) / 60 min per hr = 880 feet per min, so...10-MPH = 880 feet per minute

The diameter of the wheel is X inches. In one revolution, it travels a distance equal to the circumference of the wheel, which is Pi times the diameter:

(X inches x 3.14159) / 12 inches = Y feet (if X is 26-inches, Y = 6.81 feet)

Then we just calculate the number of revolutions needed to travel 880 feet:

(880 feet/min) / (Y feet/rev) = Z RPM (880 / 6.81 = 129.3 RPMs for 10-MPH)...which is equal to 12.9 for 1-MPH

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http://www.onlineconversion.com/

1 mph = 1.609 kph

1 kph = 0.621 mph

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29 inch tire

11.6 RPM per one-MPH

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27.5 inch tire

12.2 RPM per one-MPH

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26-inch tire

1 mph = 12.93 rpm

1 mph = 1.609 kph

1 kph = 8.10 rpm

MPH (km/h) = RPM

01__(1.61)___12.9

02__(3.22)___25.9

03__(4.83)___38.8

04__(6.44)___51.7

05__(8.05)___64.7

06__(9.65)___77.6

07__(11.26)__90.5

08__(12.87)__103.4

09__(14.48)__116.4

10__(16.09)__129.3

11___(18)___142

12___(19)___155

13___(21)___168

14___(23)___181

15___(24)___194

16___(26)___207

17___(27)___220

18___(29)___233

19___(31)___246

20___(32)___259

21___(34)___272

22___(35)___285

23___(37)___297

24___(39)___310

25___(40)___323

26___(42)___336

27___(43)___349

28___(45)___362

29___(47)___375

30___(48)___388

31___(50)___401

32___(51)___414

33___(53)___427

34___(55)___440

35___(56)___453

36___(58)___465

37___(60)___478

38___(61)___491

39___(63)___504

40___(64)___517

MPH (km/h) = RPM

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24-inch tire

1 mph = 14.00 rpm

1 mph = 1.609 km/h

1 kph = 8.80 rpm

MPH___(km/h)___RPM

01__(1.61)___14

02__(3.22)___28

03__(4.83)___42

04__(6.44)___56

05__(8.05)___70

06__(9.65)___84

07__(11.26)__98

08__(12.87)__112

09__(14.48)__126

10__(16.09)__140

11___(18)___154

12___(19)___168

13___(21)___182

14___(23)___196

15___(24)___210

16___(26)___224

17___(27)___238

18___(29)___252

19___(31)___266

20___(32)___280

21___(34)___294

22___(35)___308

23___(37)___322

24___(39)___336

25___(40)___350

26___(42)___364

27___(43)___378

28___(45)___392

29___(47)___406

30___(48)___420

31___(50)___434

32___(51)___448

33___(53)___462

34___(55)___476

35___(56)___490

36___(58)___504

37___(60)___518

38___(61)___532

39___(63)___546

40___(64)___560

MPH (km/h) = RPM

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22 inch diameter tire (Pirelli ML75 moped tire on a 20-inch rim)

15.3 RPM per one-MPH

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20-inch tire

1 mph = 16.81 rpm

1 kph = 10.50 rpm

10 mph (16 kph) = 168 rpm

11 (18) = 185

12 (19) = 202

13 (21) = 219

14 (23) = 235

15 (24) = 252

16 (26) = 269

17 (27) = 286

18 (29) = 303

19 (31) = 319

20 (32) = 336

21 (34) = 353

22 (35) = 370

23 (37) = 387

24 (39) = 403

25 (40) = 420

26 (42) = 437

27 (43) = 454

28 (45) = 471

29 (47) = 488

30 (48) = 504

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16 inch tire

21 RPM per one-MPH

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