1byte符号あり数の変換表

一応、情報工学の範囲なのでこの表も入れときます。
「2の補数」等でぐぐれば解説も出てきます。
Windows付属の電卓をうまく使えば求められますが。

16進  10進
$00 =    0
$01 =    1
$02 =    2
$03 =    3
$04 =    4
$05 =    5
$06 =    6
$07 =    7
$08 =    8
$09 =    9
$0a =   10
$0b =   11
$0c =   12
$0d =   13
$0e =   14
$0f =   15

$10 =   16
$11 =   17
$12 =   18
$13 =   19
$14 =   20
$15 =   21
$16 =   22
$17 =   23
$18 =   24
$19 =   25
$1a =   26
$1b =   27
$1c =   28
$1d =   29
$1e =   30
$1f =   31

$20 =   32
$21 =   33
$22 =   34
$23 =   35
$24 =   36
$25 =   37
$26 =   38
$27 =   39
$28 =   40
$29 =   41
$2a =   42
$2b =   43
$2c =   44
$2d =   45
$2e =   46
$2f =   47

$30 =   48
$31 =   49
$32 =   50
$33 =   51
$34 =   52
$35 =   53
$36 =   54
$37 =   55
$38 =   56
$39 =   57
$3a =   58
$3b =   59
$3c =   60
$3d =   61
$3e =   62
$3f =   63

$40 =   64
$41 =   65
$42 =   66
$43 =   67
$44 =   68
$45 =   69
$46 =   70
$47 =   71
$48 =   72
$49 =   73
$4a =   74
$4b =   75
$4c =   76
$4d =   77
$4e =   78
$4f =   79

$50 =   80
$51 =   81
$52 =   82
$53 =   83
$54 =   84
$55 =   85
$56 =   86
$57 =   87
$58 =   88
$59 =   89
$5a =   90
$5b =   91
$5c =   92
$5d =   93
$5e =   94
$5f =   95

$60 =   96
$61 =   97
$62 =   98
$63 =   99
$64 =  100
$65 =  101
$66 =  102
$67 =  103
$68 =  104
$69 =  105
$6a =  106
$6b =  107
$6c =  108
$6d =  109
$6e =  110
$6f =  111

$70 =  112
$71 =  113
$72 =  114
$73 =  115
$74 =  116
$75 =  117
$76 =  118
$77 =  119
$78 =  120
$79 =  121
$7a =  122
$7b =  123
$7c =  124
$7d =  125
$7e =  126
$7f =  127

$80 = -128
$81 = -127
$82 = -126
$83 = -125
$84 = -124
$85 = -123
$86 = -122
$87 = -121
$88 = -120
$89 = -119
$8a = -118
$8b = -117
$8c = -116
$8d = -115
$8e = -114
$8f = -113

$90 = -112
$91 = -111
$92 = -110
$93 = -109
$94 = -108
$95 = -107
$96 = -106
$97 = -105
$98 = -104
$99 = -103
$9a = -102
$9b = -101
$9c = -100
$9d =  -99
$9e =  -98
$9f =  -97

$a0 =  -96
$a1 =  -95
$a2 =  -94
$a3 =  -93
$a4 =  -92
$a5 =  -91
$a6 =  -90
$a7 =  -89
$a8 =  -88
$a9 =  -87
$aa =  -86
$ab =  -85
$ac =  -84
$ad =  -83
$ae =  -82
$af =  -81

$b0 =  -80
$b1 =  -79
$b2 =  -78
$b3 =  -77
$b4 =  -76
$b5 =  -75
$b6 =  -74
$b7 =  -73
$b8 =  -72
$b9 =  -71
$ba =  -70
$bb =  -69
$bc =  -68
$bd =  -67
$be =  -66
$bf =  -65

$c0 =  -64
$c1 =  -63
$c2 =  -62
$c3 =  -61
$c4 =  -60
$c5 =  -59
$c6 =  -58
$c7 =  -57
$c8 =  -56
$c9 =  -55
$ca =  -54
$cb =  -53
$cc =  -52
$cd =  -51
$ce =  -50
$cf =  -49

$d0 =  -48
$d1 =  -47
$d2 =  -46
$d3 =  -45
$d4 =  -44
$d5 =  -43
$d6 =  -42
$d7 =  -41
$d8 =  -40
$d9 =  -39
$da =  -38
$db =  -37
$dc =  -36
$dd =  -35
$de =  -34
$df =  -33

$e0 =  -32
$e1 =  -31
$e2 =  -30
$e3 =  -29
$e4 =  -28
$e5 =  -27
$e6 =  -26
$e7 =  -25
$e8 =  -24
$e9 =  -23
$ea =  -22
$eb =  -21
$ec =  -20
$ed =  -19
$ee =  -18
$ef =  -17

$f0 =  -16
$f1 =  -15
$f2 =  -14
$f3 =  -13
$f4 =  -12
$f5 =  -11
$f6 =  -10
$f7 =   -9
$f8 =   -8
$f9 =   -7
$fa =   -6
$fb =   -5
$fc =   -4
$fd =   -3
$fe =   -2
$ff =   -1