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What is BMI?

Surgical treatment for obesity is not for everyone who is overweight.  It is usually reserved for people who have so-called "severe obesity."

We use a tool called body mass index (BMI) to measure the level of obesity.

What does the BMI number mean?

The BMI takes both height and weight into account, so it gives a more accurate picture of body size than weight alone. In general, we use the following categories of BMI when we talk about body weight:

  • Underweight = BMI less than 18.5
  • Normal weight = BMI between 18.5 and 24.9
  • Overweight = BMI between 25 and 29.9
  • Obesity = BMI of 30 or greater
    • Class I Obesity = BMI 30-35
    • Class II Obesity = BMI 35-40
    • Class III Obesity = BMI greater than 40

In our program, we use the BMI to help us decide if someone might benefit from weight loss surgery. The surgery is not usually performed on someone with a BMI of less than 40, though there are important exceptions. For example, if there are serious medical problems related to weight, the surgery may be considered in someone with a BMI between 35 and 40. (The surgery is not done on anyone whose BMI is less than 35.)

What is my BMI?

If you'd like a precise measure of your BMI, go to the  NIH website and use the BMI calculator on line.

To use the chart below:
Find your height, in inches, in the left column. Move across and find a weight closest to your own. If your weight is lower than all the values shown next to your height, your BMI is less than 35. If you find a weight close to yours in the row next to your height, the number at the top of that column is your BMI.

Examples:

Someone who is 66 inches tall and weighs 309 pounds has a BMI of 50.

Someone who is 72 inches tall and weighs 250 pounds has a BMI of less than 35.

BMI chart, for BMI 35-54

BMI

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

Height
(inches)

Body Weight (pounds)

58

167

172

177

181

186

191

196

201

205

210

215

220

224

229

234

239

244

248

253

258

59

173

178

183

188

193

198

203

208

212

217

222

227

232

237

242

247

252

257

262

267

60

179

184

189

194

199

204

209

215

220

225

230

235

240

245

250

255

261

266

271

276

61

185

190

195

201

206

211

217

222

227

232

238

243

248

254

259

264

269

275

280

285

62

191

196

202

207

213

218

224

229

235

240

246

251

256

262

267

273

278

284

289

295

63

197

203

208

214

220

225

231

237

242

248

254

259

265

270

278

282

287

293

299

304

64

204

209

215

221

227

232

238

244

250

256

262

267

273

279

285

291

296

302

308

314

65

210

216

222

228

234

240

246

252

258

264

270

276

282

288

294

300

306

312

318

324

66

216

223

229

235

241

247

253

260

266

272

278

284

291

297

303

309

315

322

328

334

67

223

230

236

242

249

255

261

268

274

280

287

293

299

306

312

319

325

331

338

344

68

230

236

243

249

256

262

269

276

282

289

295

302

308

315

322

328

335

341

348

354

69

236

243

250

257

263

270

277

284

291

297

304

311

318

324

331

338

345

351

358

365

70

243

250

257

264

271

278

285

292

299

306

313

320

327

334

341

348

355

362

369

376

71

250

257

265

272

279

286

293

301

308

315

322

329

338

343

351

358

365

372

379

386

72

258

265

272

279

287

294

302

309

316

324

331

338

346

353

361

368

375

383

390

397

73

265

272

280

288

295

302

310

318

325

333

340

348

355

363

371

378

386

393

401

408

74

272

280

287

295

303

311

319

326

334

342

350

358

365

373

381

389

396

404

412

420

75

279

287

295

303

311

319

327

335

343

351

359

367

375

383

391

399

407

415

423

431

76

287

295

304

312

320

328

336

344

353

361

369

377

385

394

402

410

418

426

435

443

Or use this formula to calculate your own BMI:

BMI = weight in pounds x 705/height in inches squared

1. What is your weight in pounds? Write your answer ____________

2. Multiply your answer in #1 by 705. Write your answer ___________

3. What is your height in inches? Write your answer __________

4. Multiply the answer in #3 by itself. Write your answer ____________

5. Divide the answer in #2 by the answer in #4. This is your BMI.

Contact Information

Weight Loss Surgery Center
Beth Israel Deaconess Medical Center
Shapiro Clinical Center, 3rd Floor
330 Brookline Avenue
Boston, MA 02215
617.667.2845
617.667.2866
wls@bidmc.harvard.edu