Get Adobe Flash player
FacebookTwitterGoogle+
English Arabic French German Italian Portuguese Russian Spanish

Did you know?

Mobile phones will be discarded at a rate of 130 million since 2005, resulting in 65,000 tons of waste
 

Help us stay online:

small donate

resistor values The Electronic Industries Association (EIA), and other authorities, specify standard values for resistors, sometimes referred to as the "preferred value" system.  The preferred value system has its origins in the early years of the last century at a time when most resistors were carbon-graphite with relatively poor manufacturing tolerances. 

 

The rationale is simple - select values for components based on the tolerances with which they are able to be manufactured.  Using 10% tolerance devices as an example, suppose that the first preferred value is 100 ohms.  It makes little sense to produce a 105 ohm resistor since 105 ohms falls within the 10% tolerance range of the 100 ohm resistor. The next reasonable value is 120 ohms because the 100 ohm resistor with a 10% tolerance is expected to have a value somewhere between 90 and 110 ohms. The 120 ohm resistor has a value ranging between 110 and 130 ohms. Following this logic, the preferred values for 10% tolerance resistors between 100 and 1,000 ohms would be 100, 120, 150, 180, 220, 270, 330 and so on (rounded appropriately); this is the E12 series shown in the table below.

The EIA "E" series specify the preferred values for various tolerances.  The number following the "E" specifies the number of logarithmic steps per decade.  The table below is normalized for the decade between 100 and 1,000.  The values in any decade can be derived by merely dividing or multiplying the table entries by powers of 10.  The series are as follows:
E3     50% tolerance (no longer used)
E6     20% tolerance (now seldom used)
E12   10% tolerance
E24     5% tolerance
E48     2% tolerance
E96     1% tolerance
E192   0.5, 0.25, 0.1% and higher tolerances
While the "E" preferred value lists are the best way to insure one is stocking the optimum number of values for a given tolerance, a word of caution is in order with respect to what is actually available in the marketplace and certain real world practices.  For instance, the E48 list is often used as a stock list for 1% resistors for inventory control (48 values per decade rather than 96), but this practice leaves "holes" or gaps in one's stock not covered by tolerance overlap, an undesirable practice in a prototype lab (less of an issue to the digital designer than to an analog circuit designer).  The use of the E48 list for inventory control of 1% resistors works out well because every value on the E48 list just happens to also appear on the E96 list; the holes are thus symmetrical and easily filled by acquisition of one of the other 48 values per decade being omitted from stock.  However, this is not always the case as can be seen by comparing the E24 and E96 lists.  Nevertheless, many manufacturers make every single value on the E24 list in 1% tolerance even though the practice makes little mathematical sense (think about the obvious tolerance overlap between the 120 and 121 values for instance).  Stocking only the E24 series in 1% will result in less symmetrical holes in stock than the practice of stocking only the E48 series.  In any event, one should be aware of these practices to avoid confusion.


Standard EIA Decade Values Table (100 to 1,000 Decade)  

 

The Electronic Industries Association (EIA), and other authorities, specify standard values for resistors, sometimes referred to as the "preferred value" system.  The preferred value system has its origins in the early years of the last century at a time when most resistors were carbon-graphite with relatively poor manufacturing tolerances.  The rationale is simple - select values for components based on the tolerances with which they are able to be manufactured.  Using 10% tolerance devices as an example, suppose that the first preferred value is 100 ohms.  It makes little sense to produce a 105 ohm resistor since 105 ohms falls within the 10% tolerance range of the 100 ohm resistor. The next reasonable value is 120 ohms because the 100 ohm resistor with a 10% tolerance is expected to have a value somewhere between 90 and 110 ohms. The 120 ohm resistor has a value ranging between 110 and 130 ohms. Following this logic, the preferred values for 10% tolerance resistors between 100 and 1,000 ohms would be 100, 120, 150, 180, 220, 270, 330 and so on (rounded appropriately); this is the E12 series shown in the table below.

The EIA "E" series specify the preferred values for various tolerances.  The number following the "E" specifies the number of logarithmic steps per decade.  The table below is normalized for the decade between 100 and 1,000.  The values in any decade can be derived by merely dividing or multiplying the table entries by powers of 10.  The series are as follows:

E3     50% tolerance (no longer used)
E6     20% tolerance (now seldom used)
E12   10% tolerance
E24     5% tolerance
E48     2% tolerance
E96     1% tolerance
E192   0.5, 0.25, 0.1% and higher tolerances

While the "E" preferred value lists are the best way to insure one is stocking the optimum number of values for a given tolerance, a word of caution is in order with respect to what is actually available in the marketplace and certain real world practices.  For instance, the E48 list is often used as a stock list for 1% resistors for inventory control (48 values per decade rather than 96), but this practice leaves "holes" or gaps in one's stock not covered by tolerance overlap, an undesirable practice in a prototype lab (less of an issue to the digital designer than to an analog circuit designer).  The use of the E48 list for inventory control of 1% resistors works out well because every value on the E48 list just happens to also appear on the E96 list; the holes are thus symmetrical and easily filled by acquisition of one of the other 48 values per decade being omitted from stock.  However, this is not always the case as can be seen by comparing the E24 and E96 lists.  Nevertheless, many manufacturers make every single value on the E24 list in 1% tolerance even though the practice makes little mathematical sense (think about the obvious tolerance overlap between the 120 and 121 values for instance).  Stocking only the E24 series in 1% will result in less symmetrical holes in stock than the practice of stocking only the E48 series.  In any event, one should be aware of these practices to avoid confusion.

Standard EIA Decade Values Table (100 to 1,000 Decade)

 
   

 

E6

E12

E24

E48

E96

E192

100

100

100

100

100

100

101

102

102

104

105

105

105

106

107

107

109

110

110

110

110

111

113

113

114

115

115

115

117

118

118

120

120

120

121

121

121

123

124

124

126

127

127

127

129

130

130

132

130

133

133

133

135

137

137

138

140

140

140

142

143

143

145

150

150

150

147

147

147

149

150

150

152

154

154

154

156

158

158

160

160

162

162

162

164

165

165

167

169

169

169

172

174

174

176

180

180

178

178

178

180

182

182

184

187

187

187

189

191

191

193

200

196

196

196

198

200

200

203

205

205

205

208

210

210

213

E6

E12

E24

E48

E96

E192

220

220

220

215

215

215

218

221

221

223

226

226

226

229

232

232

234

240

237

237

237

240

243

243

246

249

249

249

252

255

255

258

270

270

261

261

261

264

267

267

271

274

274

274

277

280

280

284

300

287

287

287

291

294

294

298

301

301

301

305

309

309

312

330

330

330

316

316

316

320

324

324

328

332

332

332

336

340

340

344

360

348

348

348

352

357

357

361

365

365

365

370

374

374

379

390

390

383

383

383

388

392

392

397

402

402

402

407

412

412

417

430

422

422

422

427

432

432

437

442

442

442

448

453

453

459

E6

E12

E24

E48

E96

E192

470

470

470

464

464

464

470

475

475

481

487

487

487

493

499

499

505

510

511

511

511

517

523

523

530

536

536

536

542

549

549

556

560

560

562

562

562

569

576

576

583

590

590

590

597

604

604

612

620

619

619

619

626

634

634

642

649

649

649

657

665

665

673

680

680

680

681

681

681

690

698

698

706

715

715

715

723

732

732

741

750

750

750

750

759

768

768

777

787

787

787

796

806

806

816

820

820

825

825

825

835

845

845

856

866

866

866

876

887

887

898

910

909

909

909

920

931

931

942

953

953

953

965

976

976

988

Text taken from logwell.com