Ten thousand steps is five miles. It is printed on step-challenge posters, repeated in walking groups and built into more weekly plans than anyone could count. It is also wrong for most people who walk it. For a woman of 5'4", close to the average US height for women in CDC body measurements, 10,000 walking steps cover 4.17 miles. For a man of 5'9", close to the average for men, 4.52. Five miles takes about two thousand steps more than the poster says.
That one rounded number is where this article starts. What follows is a lean-week plan, the kind written on a Sunday evening from three numbers everyone has heard, and then counted line by line. Nobody in particular wrote it; it is assembled from the shortcuts that show up again and again. Each line went through one calculator, and seven of its assumptions did not survive.
The plan, as it was first written
The goal was modest: keep weight steady, lose a little fat, keep the muscle. The plan had three parts.
Walking: 10,000 steps every day, "which is 5 miles and about 360 extra calories." A brisk pace on most days, because faster walking surely burns a lot more.
Eating: 16:8 intermittent fasting, last meal finished at 8:00 PM, so the window would open at noon. A run at 7:00 AM before work. Bed at 10:30 PM.
Body composition: a 5'10" man at 180 lb, 15% body fat by his bathroom scale, read online that his FFMI of 22 was "close to the natural limit" and planned a cut to 170 lb to "push it toward 25."
Every line sounds reasonable. Three of them are arithmetic that can be checked in a minute, and the other four depend on what the numbers actually mean. Here is the count.
Counting it, number by number
The steps
The steps to miles calculator needs a step length, and when nobody has measured one it uses the convention pedometers rely on: a walking step of 0.413 of height for women and 0.415 for men. At 5'4" that is a 26.4-inch step, 2,397 steps to a mile, and 10,000 steps come to 4.17 miles, or 6.71 km. The factor is a convention, not a law; in a gait study of 313 adults published in Sensors the mean step ran from 0.62 m for people 141 to 150 cm tall to 0.91 m at 191 to 200 cm, with a wide spread inside each group. But it is close enough to show that the poster is generous.
| Walker | 10,000 steps | Steps for 5 miles |
|---|---|---|
| Woman, 5'0" | 3.91 miles | 12,785 |
| Woman, 5'4" | 4.17 miles | 11,985 |
| Woman, 5'8" | 4.43 miles | 11,280 |
| Man, 5'6" | 4.32 miles | 11,566 |
| Man, 5'9" | 4.52 miles | 11,063 |
| Man, 6'0" | 4.72 miles | 10,602 |
| Man, 6'4" | 4.98 miles | 10,044 |
Read across a row and the problem is plain. Only walkers well over six feet get near five miles from 10,000 steps, and even at 6'4" it is 4.98. A 5'0" walker needs 12,785 steps for the same five miles.
The calories need the same care. The calculator takes its METs from the Adult Compendium of Physical Activities, where one MET is defined as 1 calorie per kilogram per hour, the cost of sitting quietly. At 3.0 mph the Compendium gives walking 3.8 METs, so a 150 lb walker spends about 360 calories over the 1 h 23 min. That is the total for the walk, though, and the body would have burned one MET of it sitting on the couch. The part the walk adds is about 265.
| Pace | METs | Time for 10,000 steps | Calories, 150 lb |
|---|---|---|---|
| 2.5 mph | 3.0 | 1 h 40 min | 341 |
| 3.0 mph | 3.8 | 1 h 23 min | 360 |
| 3.5 mph | 4.8 | 1 h 12 min | 389 |
| 4.0 mph | 5.5 | 1 h 3 min | 390 |
And the pace? Going from 2.5 to 4.0 mph takes the same 10,000 steps from 341 to 390 calories, 49 more, or about 14 percent, while the time drops by 37 minutes. Faster walking is worth it for the time it saves. It is not a calorie multiplier.
The fasting day
The intermittent fasting calculator takes the protocol and the time the last meal is finished, then works backwards. With 16:8 and dinner done at 8:00 PM, the window runs from 12:00 PM to 8:00 PM, with meals at 12:00, 4:00 and 7:30. So far, so good. The other two entries in the plan are where it breaks.
The 7:00 AM run falls in the middle of the fast, eleven hours after the last meal and five before the next. Cleveland Clinic advises exercising before or after a fast rather than during it, when you can still drink and refuel. The calculator says which last-meal times would fix it: anything from 7:00 AM to 3:00 PM would bring the run inside the window, none of which suits a family dinner. Moving the run is easier than moving the meals.
Bed at 10:30 PM is the second problem. Cleveland Clinic suggests starting the fast at least three hours before bedtime; dinner finished at 8:00 PM leaves 2 h 30 min. Half an hour is all it takes: finish the last meal by 7:30 PM.
One thing the plan got right without knowing it. Cleveland Clinic calls 14:10 and 16:8 the safer bet for a first try at intermittent fasting. A plan that had started with one meal a day would have opened a single 7:00 to 8:00 PM window and fasted 23 hours from the start.
The FFMI
FFMI, the fat-free mass index, divides fat-free mass by height squared; the normalized version adds 6.3 x (1.80 - height in meters) so every height compares with a 1.80 m man, the correction Kouri and colleagues used when they introduced the index. The FFMI calculator takes weight, height and body fat. At 5'10", 180 lb and 15%, the man in the plan carries 153.0 lb of fat-free mass, a normalized FFMI of 22.1.
Is 22 "close to the natural limit"? In Kouri's study of 157 male athletes, the normalized FFMI of those who had never used steroids reached up to 25.0, a finding the authors called preliminary. The man is 2.9 points below that line and 3.1 above the median of 18.9 that Schutz and colleagues measured in young Swiss men. Muscular, then, with room to grow.
The cut is where the plan misreads the index. FFMI counts only fat-free mass, so losing fat cannot move it:
| Week | Weight | Body fat | Fat-free mass | FFMI |
|---|---|---|---|---|
| Start | 180 lb | 15% | 153.0 lb | 22.1 |
| After a clean cut | 170 lb | 10% | 153.0 lb | 22.1 |
| After a lean bulk instead | 190 lb | 15% | 161.5 lb | 23.3 |
| Start, scale reads 12% | 180 lb | 12% | 158.4 lb | 22.9 |
A clean cut to 170 lb at 10% leaves fat-free mass at 153.0 lb and FFMI at 22.1, exactly where it started. Reaching 25.0 at this height would take 173.3 lb of fat-free mass, 20.3 lb more than now; only the lean bulk in the third row moves the number at all. The last row is the other trap. If the bathroom scale reads 12% when the truth is 15%, FFMI comes out at 22.9, a gain of 0.8 that no training produced.
Seven mistakes, and what each one cost
The whole plan, assumption by assumption, next to the count:
| # | What the plan assumed | What the count says |
|---|---|---|
| 1 | 10,000 steps a day is 5 miles | 4.17 miles at 5'4", 4.52 at 5'9"; 5 miles takes 11,985 or 11,063 steps |
| 2 | the walk burns 360 extra calories | 360 is the total; about 265 above what the body burns at rest |
| 3 | walking faster burns far more | same 10,000 steps: 341 calories at 2.5 mph, 390 at 4.0 mph |
| 4 | a 7 AM run fits a noon-to-8 window | it falls in the middle of the fast |
| 5 | dinner at 8, bed at 10:30 is fine | only 2 h 30 min; the last meal belongs before 7:30 PM |
| 6 | the cut will push FFMI up toward 25 | FFMI stays at 22.1; 25.0 needs 20.3 lb more fat-free mass |
| 7 | the scale's 15% is the number | 3 points either way moves FFMI from 21.3 to 22.9 |
None of the seven is exotic. The first three come from treating a convenient figure as if it were measured. The fourth and fifth come from placing two fixed events, a run and a bedtime, without looking at where the window put them. The last two come from reading an index without asking what goes into it.
The costs are small one day at a time and large over a season. Walking 10,000 steps believing they are 5 miles leaves the plan about 0.8 miles short every day at 5'4". Counting the 360 calories as extra overstates the walk by about 95 calories a day. And a cut planned to raise FFMI ends, after weeks of effort, with the same 22.1 and a sense that something failed when nothing did.
The plan, rewritten
Walking: 10,000 steps, called what they are, 4.17 miles. On days when five miles is the goal, walk 11,985 steps, or better, measure a step once: walk 20 normal steps, measure the distance and divide by 20, then enter that step in place of the estimate. Pace for time, not for calories; book about 265 extra calories at 3.0 mph, not 360.
Eating: 16:8, last meal finished at 7:30 PM, so the window runs from 11:30 AM to 7:30 PM and the fast starts three hours before a 10:30 PM bedtime. The run moves to 5:30 PM, inside the window, with dinner still to come after it.
Body composition: the cut stays if the goal is less fat, but the FFMI target goes. Track fat-free mass instead, measured the same way, at the same time of day, every time; if the number to beat is 22.1, it moves only when lean mass does.
Five rules for the next plan
- Ask where a round number came from. 10,000 steps, 5 miles and 25.0 are all real numbers with a context. The context is height for the first two and a single study of men for the third.
- Ask what a calorie figure includes. MET-based calories are totals. Subtract one MET for the part the body burns anyway.
- Put the fixed events on the clock before choosing the window. The workout and the bedtime decide where an eating window can sit, not the other way around.
- Keep three hours between the last meal and bed. It is the simplest fasting rule to check and the easiest to miss.
- Read an index by its inputs. FFMI rises only with fat-free mass and is only as accurate as the body fat number under it.
Fasting is not right for everyone. Cleveland Clinic names people who are pregnant or nursing, malnourished, with hypoglycemia or with certain chronic diseases, and children; with a history of an eating disorder, any fast belongs under medical supervision.
Tools discussed in this article
- Intermittent Fasting Calculator - the eating window, meal times and next opening for 14:10, 16:8, 18:6, 20:4, OMAD and 5:2, with a check on the workout and the bedtime.
- Steps to Miles Calculator - steps to miles and km or a distance to steps, from height and sex or a measured step, with walking time and calories.
- FFMI Calculator - the raw and normalized fat-free mass index against the ESPEN low cut-off, the population median and the Kouri limit.
Ready-made calculations from this article
16:8 intermittent fasting from... 8 AM to 4 PM, 9 AM to 5 PM, 10 AM to 6 PM, 11 AM to 7 PM, 12 PM to 8 PM, 1 PM to 9 PM
Intermittent fasting schedules: 14:10, 18:6, 20:4, OMAD
How many miles is this many steps for a woman (5'4")? 3,000, 4,000, 5,000, 6,000, 7,000, 7,500, 8,000, 9,000, 10,000, 12,000, 15,000, 20,000, 25,000, 30,000
How many miles is this many steps for a man (5'9")? 3,000, 4,000, 5,000, 6,000, 7,000, 7,500, 8,000, 9,000, 10,000, 12,000, 15,000, 20,000, 25,000, 30,000
Steps in a mile for a woman of: 5'0, 5'1, 5'2, 5'3, 5'4, 5'5, 5'6, 5'7, 5'8, 5'9
Steps in a mile for a man of: 5'3, 5'4, 5'5, 5'6, 5'7, 5'8, 5'9, 5'10, 5'11, 6 foot, 6'1, 6'2, 6'3, 6'4
How many steps is... half a mile, 1.5 miles, 2 miles, 3 miles, 4 miles, 5 miles, 6 miles, 10 miles, 1 km, 2 km, 3 km, a 5K walk, a 10K walk
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