In a signed binary, the first bit (the leftmost) is reserved for the sign,
1 = negative, 0 = positive. This bit does not count when calculating the absolute value.
2. Construct the unsigned binary number.
Exclude the first bit (the leftmost), that is reserved for the sign:
1000 0101 0101 0001 1000 1100 0010 1010 1111 1001 0111 1001 0101 0000 1111 1111 = 000 0101 0101 0001 1000 1100 0010 1010 1111 1001 0111 1001 0101 0000 1111 1111
3. Map the unsigned binary number's digits versus the corresponding powers of 2 that their place value represent:
262
0 261
0 260
0 259
0 258
1 257
0 256
1 255
0 254
1 253
0 252
1 251
0 250
0 249
0 248
1 247
1 246
0 245
0 244
0 243
1 242
1 241
0 240
0 239
0 238
0 237
1 236
0 235
1 234
0 233
1 232
0 231
1 230
1 229
1 228
1 227
1 226
0 225
0 224
1 223
0 222
1 221
1 220
1 219
1 218
0 217
0 216
1 215
0 214
1 213
0 212
1 211
0 210
0 29
0 28
0 27
1 26
1 25
1 24
1 23
1 22
1 21
1 20
1
4. Multiply each bit by its corresponding power of 2 and add all the terms up.
000 0101 0101 0001 1000 1100 0010 1010 1111 1001 0111 1001 0101 0000 1111 1111(2) =
(0 × 262 + 0 × 261 + 0 × 260 + 0 × 259 + 1 × 258 + 0 × 257 + 1 × 256 + 0 × 255 + 1 × 254 + 0 × 253 + 1 × 252 + 0 × 251 + 0 × 250 + 0 × 249 + 1 × 248 + 1 × 247 + 0 × 246 + 0 × 245 + 0 × 244 + 1 × 243 + 1 × 242 + 0 × 241 + 0 × 240 + 0 × 239 + 0 × 238 + 1 × 237 + 0 × 236 + 1 × 235 + 0 × 234 + 1 × 233 + 0 × 232 + 1 × 231 + 1 × 230 + 1 × 229 + 1 × 228 + 1 × 227 + 0 × 226 + 0 × 225 + 1 × 224 + 0 × 223 + 1 × 222 + 1 × 221 + 1 × 220 + 1 × 219 + 0 × 218 + 0 × 217 + 1 × 216 + 0 × 215 + 1 × 214 + 0 × 213 + 1 × 212 + 0 × 211 + 0 × 210 + 0 × 29 + 0 × 28 + 1 × 27 + 1 × 26 + 1 × 25 + 1 × 24 + 1 × 23 + 1 × 22 + 1 × 21 + 1 × 20)(10) =
(0 + 0 + 0 + 0 + 288 230 376 151 711 744 + 0 + 72 057 594 037 927 936 + 0 + 18 014 398 509 481 984 + 0 + 4 503 599 627 370 496 + 0 + 0 + 0 + 281 474 976 710 656 + 140 737 488 355 328 + 0 + 0 + 0 + 8 796 093 022 208 + 4 398 046 511 104 + 0 + 0 + 0 + 0 + 137 438 953 472 + 0 + 34 359 738 368 + 0 + 8 589 934 592 + 0 + 2 147 483 648 + 1 073 741 824 + 536 870 912 + 268 435 456 + 134 217 728 + 0 + 0 + 16 777 216 + 0 + 4 194 304 + 2 097 152 + 1 048 576 + 524 288 + 0 + 0 + 65 536 + 0 + 16 384 + 0 + 4 096 + 0 + 0 + 0 + 0 + 128 + 64 + 32 + 16 + 8 + 4 + 2 + 1)(10) =
(288 230 376 151 711 744 + 72 057 594 037 927 936 + 18 014 398 509 481 984 + 4 503 599 627 370 496 + 281 474 976 710 656 + 140 737 488 355 328 + 8 796 093 022 208 + 4 398 046 511 104 + 137 438 953 472 + 34 359 738 368 + 8 589 934 592 + 2 147 483 648 + 1 073 741 824 + 536 870 912 + 268 435 456 + 134 217 728 + 16 777 216 + 4 194 304 + 2 097 152 + 1 048 576 + 524 288 + 65 536 + 16 384 + 4 096 + 128 + 64 + 32 + 16 + 8 + 4 + 2 + 1)(10) =
383 241 559 505 195 263(10)
5. If needed, adjust the sign of the integer number by the first digit (leftmost) of the signed binary:
1000 0101 0101 0001 1000 1100 0010 1010 1111 1001 0111 1001 0101 0000 1111 1111(2) = -383 241 559 505 195 263(10)
The number 1000 0101 0101 0001 1000 1100 0010 1010 1111 1001 0111 1001 0101 0000 1111 1111(2) converted from a signed binary (base two) and written as an integer in decimal system (base ten):
1000 0101 0101 0001 1000 1100 0010 1010 1111 1001 0111 1001 0101 0000 1111 1111(2) = -383 241 559 505 195 263(10)
Spaces were used to group digits: for binary, by 4, for decimal, by 3.