Slot Car Gear Ratio Calculator

Calculating your own gear ratios or rollout is actually quite simple, (G / P) * D where G is the number of teeth of your spur or crown gear, and P is the number of teeth on the pinion gear, and D is the diameter of your rear tire (in decimal inches). For example for a 12 tooth pinion with a 37 tooth spur and a tire size of .700 the calculation would be: 12 / 37 * .700 is 2.16:1 which means for every 1 full revolution of your rear tires the motor will make 2.16 revolutions.

Usage: This chart will allow you to calculate the gear ratios or rollout for Slotcars. Only available ratios will be shown based on what size and pitch gears are available (the white spaces with numbers. Enter the number in Decimal Inches, Fractions, or Millimeters and click the Calculate button, then use your mouse to highlight the pinion gear on the top, and the spur or crown gear on the left. For ratios only use 1.00 for the tire size (or leave blank for default).

Tire:		Pinion Gears															Axle Bore
1.000"		5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	3/32	1/8	2mm
48	26		4.33	3.71	3.25	2.89	2.60	2.36	2.17	2.00	1.86							✓	✓
	27		4.50	3.86	3.38	3.00	2.70	2.45	2.25	2.08	1.93							✓	✓
	28		4.67	4.00	3.50	3.11	2.80	2.55	2.33	2.15	2.00							✓	✓
	29		4.83	4.14	3.63	3.22	2.90	2.64	2.42	2.23	2.07							✓	✓
	30		5.00	4.29	3.75	3.33	3.00	2.73	2.50	2.31	2.14								✓
	31		5.17	4.43	3.88	3.44	3.10	2.82	2.58	2.38	2.21								✓
	32		5.33	4.57	4.00	3.56	3.20	2.91	2.67	2.46	2.29								✓
	33		5.50	4.71	4.13	3.67	3.30	3.00	2.75	2.54	2.36								✓
	34		5.67	4.86	4.25	3.78	3.40	3.09	2.83	2.62	2.43								✓
64	32	6.40			4.00	3.56	3.20	2.91	2.67	2.46	2.29	2.13	2.00	1.88	1.78	1.68	1.60	✓
	34	6.80			4.25	3.78	3.40	3.09	2.83	2.62	2.43	2.27	2.13	2.00	1.89	1.79	1.70	✓
	35	7.00			4.38	3.89	3.50	3.18	2.92	2.69	2.50	2.33	2.19	2.06	1.94	1.84	1.75	✓
	36	7.20			4.50	4.00	3.60	3.27	3.00	2.77	2.57	2.40	2.25	2.12	2.00	1.89	1.80	✓
	37	7.40			4.63	4.11	3.70	3.36	3.08	2.85	2.64	2.47	2.31	2.18	2.06	1.95	1.85	✓
	38	7.60			4.75	4.22	3.80	3.45	3.17	2.92	2.71	2.53	2.38	2.24	2.11	2.00	1.90	✓
	39	7.80			4.88	4.33	3.90	3.55	3.25	3.00	2.79	2.60	2.44	2.29	2.17	2.05	1.95	✓
	40	8.00			5.00	4.44	4.00	3.64	3.33	3.08	2.86	2.67	2.50	2.35	2.22	2.11	2.00	✓
	46	9.20			5.75	5.11	4.60	4.18	3.83	3.54	3.29	3.07	2.88	2.71	2.56	2.42	2.30	✓
	48	9.60			6.00	5.33	4.80	4.36	4.00	3.69	3.43	3.20	3.00	2.82	2.67	2.53	2.40	✓
	50	10.00			6.25	5.56	5.00	4.55	4.17	3.85	3.57	3.33	3.13	2.94	2.78	2.63	2.50	✓
	52	10.40			6.50	5.78	5.20	4.73	4.33	4.00	3.71	3.47	3.25	3.06	2.89	2.74	2.60	✓
	54	10.80			6.75	6.00	5.40	4.91	4.50	4.15	3.86	3.60	3.38	3.18	3.00	2.84	2.70	✓
	56	11.20			7.00	6.22	5.60	5.09	4.67	4.31	4.00	3.73	3.50	3.29	3.11	2.95	2.80	✓
	58	11.60			7.25	6.44	5.80	5.27	4.83	4.46	4.14	3.87	3.63	3.41	3.22	3.05	2.90	✓
	60	12.00			7.50	6.67	6.00	5.45	5.00	4.62	4.29	4.00	3.75	3.53	3.33	3.16	3.00	✓
	62	12.40			7.75	6.89	6.20	5.64	5.17	4.77	4.43	4.13	3.88	3.65	3.44	3.26	3.10	✓
72	30	6.00	5.00	4.29	3.75	3.33	3.00	2.73	2.50	2.31	2.14	2.00						✓		✓
	33	6.60	5.50	4.71	4.13	3.67	3.30	3.00	2.75	2.54	2.36	2.20						✓		✓
	37	7.40	6.17	5.29	4.63	4.11	3.70	3.36	3.08	2.85	2.64	2.47						✓
	38	7.60	6.33	5.43	4.75	4.22	3.80	3.45	3.17	2.92	2.71	2.53						✓		✓
	39	7.80	6.50	5.57	4.88	4.33	3.90	3.55	3.25	3.00	2.79	2.60						✓
	40	8.00	6.67	5.71	5.00	4.44	4.00	3.64	3.33	3.08	2.86	2.67						✓		✓
	41	8.20	6.83	5.86	5.13	4.56	4.10	3.73	3.42	3.15	2.93	2.73						✓
	42	8.40	7.00	6.00	5.25	4.67	4.20	3.82	3.50	3.23	3.00	2.80						✓		✓
	43	8.60	7.17	6.14	5.38	4.78	4.30	3.91	3.58	3.31	3.07	2.87						✓		✓
	44	8.80	7.33	6.29	5.50	4.89	4.40	4.00	3.67	3.38	3.14	2.93						✓		✓
80	43		7.17	6.14	5.38													✓		✓
	44		7.33	6.29	5.50													✓		✓
	45		7.50	6.43	5.63													✓		✓
	46		7.67	6.57	5.75													✓		✓