Calculating the resistance of a thermistor
B or beta value is the thermal exponent of the NTC thermistor, which is defined as the ratio of the difference between the napierian logarithms of the zero power resistance at two temperatures to the difference between the reciprocals of the two temperatures.

You can calculate the RT2 using this formula:

Here:

B = 3380   
T1 = 298.15 K (25°C)
RT1 = 10Kohm
T1 and T2 are expressed in K with T(K) = T(°C) + 273.15
3KΩ
5KΩ
5KΩ
5KΩ
10KΩ
10KΩ
10KΩ
-30°C
31.70
52.84
63.73
90.83
111.3
127.5
133.6250
-25°C
24.75
41.19
48.60
66.65
86.39
97.10
101.6000
-20°C
19.46
32.44
37.40
49.44
67.74
74.80
77.9250
-15°C
15.41
25.65
29.03
37.05
53.39
58.08
60.2925
-10°C
12.29
20.48
22.72
28.03
42.45
45.44
47.0150
-5°C
9.864
16.43
17.91
21.40
33.89
35.82
36.9450
0°C
7.974
13.29
14.23
16.48
27.28
28.46
29.2350
5°C
6.486
10.80
11.39
12.79
22.05
22.78
23.3050
10°C
5.303
8.839
9.181
9.998
17.96
18.36
18.6850
15°C
4.362
7.266
7.451
7.879
14.68
14.90
15.0875
20°C
3.608
6.013
6.085
6.255
12.09
12.17
12.2450
25°C
3.000
5.000
5.000
5.000
10.00
10.00
10.0000
30°C
2.507
4.179
4.132
4.024
8.313
8.264
7.9340
35°C
2.106
3.508
3.434
3.259
6.941
6.890
6.7738
40°C
1.777
2.962
2.869
2.656
5.828
5.738
5.6230
45°C
1.507
2.510
2.407
2.177
4.912
4.810
4.6913
50°C
1.283
2.138
2.032
1.794
4.161
4.064
3.9265
55°C
1.096
1.826
1.723
1.487
3.537
3.448
3.3043
60°C
0.9408
1.568
1.467
1.238
3.021
2.934
2.7928
65°C
0.8106
1.351
1.253
1.036
2.589
2.504
2.3726
70°C
0.7014
1.169
1.073
0.8717
2.229
2.146
2.0210
75°C
0.6090
1.014
0.9225
0.7364
1.924
1.845
1.7288
80°C
0.5303
0.8838
0.7959
0.6248
1.669
1.592
1.4858
85°C
0.4634
0.7725
0.6887
0.5324
1.451
1.378
1.2818
90°C
0.4064
0.6774
0.5975
0.4555
1.266
1.195
1.1088
95°C
0.3578
0.5963
0.5196
0.3912
1.108
1.039
0.9640
100°C
0.3160
0.5267
0.4533
0.3372
0.9735
0.966
0.8377
105°C
0.2798
0.4656
0.3974
0.2918
0.8574
0.7949
0.7344
110°C
0.2478
0.4130
0.3514
0.2533
0.7579
0.7028
0.6429
B25/50°C
3270
3270
3470
3950
3380
3470
3600
B25/85°C
3320
3320
3530
3990
3435
3530
3630
10K Ω 50K Ω 100K Ω 50KΩ 50K Ω 100K Ω 100K Ω 150K Ω
-30°C 181.7 908.3 1790 967.33 991.35 1984.3 2056.7 3942.8
-25°C 133.5 667.6 1321 705.35 723.36 1447.7 1502.2 2787.1
-20°C 98.99 494.4 984.7 519.86 533.09 1066.9 1107.0 1992.8
-15°C 74.06 370.3 740.8 387.07 396.64 793.70 822.68 1440.3
-10°C 56.06 280.3 562.3 290.98 297.80 595.85 616.42 1051.9
-5°C 42.81 214.1 430.5 220.79 225.57 451.25 465.45 775.83
0°C 32.96 164.8 332.3 173.34 172.0 344.1 352.4 576.7
5°C 25.57 127.9 257.5 132.79 132.2 264.3 270.0 433.2
10°C 20.00 99.98 201.1 102.68 102.4 204.8 208.3 328.4
15°C 15.76 78.79 158.2 80.11 80.03 160.1 161.9 250.9
20°C 12.51 62.55 125.4 63.04 63.00 126.0 126.7 193.3
25°C 10.00 50.00 100.0 50.00 50.00 100.0 100.0 150.0
30°C 8.048 40.24 80.29 39.96 39.76 79.51 78.35 117.3
35°C 6.517 32.58 64.87 32.18 31.89 63.77 62.37 92.28
40°C 5.321 26.56 57.72 26.09 25.73 51.45 49.94 73.11
45°C 4.356 21.78 43.10 21.29 20.88 41.76 40.22 58.28
50°C 3.588 17.94 35.42 17.48 17.04 34.08 32.56 46.74
55°C 2.972 14.86 29.26 14.44 13.999 27.97 26.40 37.71
60°C 2.467 12.38 24.30 12.00 11.53 23.06 21.53 30.58
65°C 2.073 10.36 20.27 10.03 9.541 19.8 17.69 24.94
70°C 1.734 8.717 16.99 8.42 7.929 15.86 14.62 20.45
75°C 1.473 7.364 14.31 7.11 6.621 13.24 12.10 16.85
80°C 1.250 6.248 12.10 6.03 5.552 11.10 10.05 13.94
85°C 1.065 5.324 10.27 5.05 4.674 9.348 8.376 11.60
90°C 0.911 4.555 8.758 4.40 3.950 7.900 7.004 9.680
95°C 0.7824 3.912 7.459 3.78 3.349 6.698 5.894 8.118
100°C 0.6744 3.372 6.438 3.26 2.849 5.698 4.978 6.836
105°C 0.5834 2.917 5.550 2.82 2.438 4.875 4.215 5.780
110°C 0.5066 2.533 4.801 2.46 2.093 4.186 3.580 4.904
B25/50°C 3950 3950 4000 4050 4150 4150 4300 4500
B25/80°C 3990 3990 4050 4080 4220 4220 4410 4560