Schofield Equation Calculator

All ten Schofield equations

There is no single Schofield equation. There are ten: one per sex for each of five age bands. Weight goes in, kilocalories per day come out, and nothing else is asked for.

W is body weight in kilograms and every result is kilocalories per day. Read down the men’s column and you can watch the slope fall: a kilogram of a nine-year-old costs 22.7 kcal a day at rest, the same kilogram of a fifty-year-old costs 11.5.

How the calculator applies it

1. 1. Convert weight to kilograms

   weight in kg = lb × 0.453592

2. 2. Pick the equation for your sex and age band

   a 30-year-old man falls in 30 to 59, so BMR = (11.472 × W) + 873.1

3. 3. Round to a whole calorie

   BMR = round(BMR)

Why two Schofield calculators disagree

Two printings of these equations are in circulation. Schofield published coefficients to three decimal places. The FAO/WHO/UNU report that adopted them printed rounded versions, so 11.472 × W + 873.1 became 11.5 × W + 873.

For most people that rounding is worth a couple of kilocalories. In the oldest band it is not: the rounded printing for men over 60 is 11.9 × W + 700 against Schofield’s 11.711 × W + 587.7, and at 75 kg those give 1,593 and 1,466 kcal, a gap of 127.

This calculator uses Schofield’s own coefficients and shows what the rounded printing would have said underneath, so you can see which version a different tool is running rather than wondering why its number differs from this one.

Schofield or Mifflin-St Jeor?

Mifflin-St Jeor is the usual choice on consumer sites and is what the BMR calculator here uses. Schofield is the usual choice in clinical and public health work, because the FAO/WHO/UNU adopted it for setting energy requirements. The two are close for younger adults and separate as people age, largely because Schofield ignores height while Mifflin-St Jeor does not.

The 70-year-old woman is the case worth looking at: 1,097 kcal by Mifflin-St Jeor and 1,222 by Schofield, 125 apart for the same person. Neither is the truth. They are two lines fitted through two different sets of people, and the variation between calculators is the thing to keep in view rather than any single figure.

Where the equations came from

Schofield reviewed the published BMR literature for the FAO/WHO/UNU expert consultation that met in Rome in 1981, and the equations he produced became the basis of the 1985 FAO/WHO/UNU report on energy and protein requirements. That is why they are still standard in clinical and public health work rather than on consumer sites.

The known weakness is who was in that database. Of its 7,173 BMR values, 3,388 were Italian subjects, 47% of the total, and relatively few came from the tropics. Reviewing the studies published between 1980 and 2000, Henry found that the FAO/WHO/UNU equations overestimate BMR in many communities, and built a replacement set from 10,552 values with the Italian subjects excluded. Treat the output as the planning figure it was designed to be rather than a measurement of your own metabolism.

Whatever equation you start from, resting metabolism is only the base. To reach a daily total you multiply it by an activity factor, which the TDEE calculator does, and that choice moves the answer far more than the choice of BMR equation does.