12-3-30 treadmill workout calculator
Written by Jamie Miller, Founder & EditorLast checked
12% incline, 3 mph (4.8 km/h), 30 minutes. That is 2.41 km and about 288 m of climb.
Work it out for your weight
12-3-30 workout settings
The name is the setting list: 12% incline, 3 mph, 30 minutes.
12-3-30 in km/h
3 mph is 4.828 km/h, so a console stepping in tenths takes 4.8. Over 30 minutes that is 2.41 km, or 1.5 miles. The speed converter does any other setting.
Height climbed depends on which distance you mean. Along the belt, which is what the machine reports and what this page uses, the rise is 288 m. Treating the 2.41 km as horizontal gives 290 m.
12 3 30 UK: which treadmills reach 12% incline
Of the 13 treadmills we hold sourced records for, 9 publish a maximum incline and 4 of those reach 12% or more. The other 4 publish no incline figure at all, so they are counted separately rather than assumed either way. Not established, checked 19 Sept 2026
| Machine | Maximum incline | Reaches 12% |
|---|---|---|
| Reebok Jet 100z | 15% | Yes |
| JTX Sprint-7 | 12% | Yes |
| JTX Sprint-8 Pro | 12% | Yes |
| NordicTrack Commercial 1750 | 12% | Yes |
| JTX Sprint-9 Pro | 11% | No |
| Horizon 5.0AT | 10% | No |
| JTX RunRise | 10% | No |
| ProForm Carbon TL | 10% | No |
| JTX SlimLine | 0% | No |
Each figure is from that machine's own record, with its source and date on its review page. A machine that cannot reach 12% cannot do this workout as named, which is worth knowing before buying one for it.
Calories in a 12-3-30 workout
About 325 kcal for a 75 kg walker, or 277 to 374 once you allow for the fact that this is a population equation applied to one person. It is an estimate from a published formula, not a measurement, and nothing here is advice about weight or health.
| Body weight | METs | Estimate | Range |
|---|---|---|---|
| 55 kg | 8.3 | 239 kcal | 203 to 274 kcal |
| 60 kg | 8.3 | 260 kcal | 221 to 299 kcal |
| 65 kg | 8.3 | 282 kcal | 240 to 324 kcal |
| 70 kg | 8.3 | 304 kcal | 258 to 349 kcal |
| 75 kg | 8.3 | 325 kcal | 277 to 374 kcal |
| 80 kg | 8.3 | 347 kcal | 295 to 399 kcal |
| 85 kg | 8.3 | 369 kcal | 314 to 424 kcal |
| 90 kg | 8.3 | 391 kcal | 332 to 449 kcal |
| 95 kg | 8.3 | 412 kcal | 350 to 474 kcal |
| 100 kg | 8.3 | 434 kcal | 369 to 499 kcal |
The incline is doing most of the work in these figures: the same 30 minutes at 4.8 km/h on the flat comes to about 130 kcal at 75 kg, by this same equation.
That flat figure will not match our calorie calculator, and the difference is real rather than a mistake. Two published methods disagree about the same walk: the 2024 Compendium gives 3.8 METs for a 3 mph (4.8 km/h) treadmill walk and the ACSM equation gives 3.3, about 15% apart. This page uses the ACSM equation throughout, because it is the only one of the two that takes an incline at all. The calorie calculator leads with the Compendium and says the same thing.
How this is calculated
Distance is speed x time. Climb is distance x sin(arctan(grade)), which is the rise when the distance is measured along the slope, as a treadmill measures it.
Calories use the ACSM walking equation: VO2 = speed x 0.1 + grade x speed x 1.8 + 3.5, with speed in metres a minute and grade as a fraction. METs are VO2 divided by 3.5, and kcal a minute is METs x 3.5 x kg / 200.
The equation is sourced; the speeds it is valid over are not. The range quoted everywhere, about 1.9 to 3.7 mph for walking, traces to a site that names no edition of the ACSM guidelines. So this calculator stops at 5.95 km/h and returns nothing above it rather than extrapolating past a boundary nobody has shown us. 3 mph sits inside that band, which is why this page can use it at all.
The range is the mid figure plus and minus 15%, a plain acknowledgement that a population equation applied to one person is approximate. It is not a confidence interval.
Sources
- Publisher stated, Independent publication
- The ACSM walking and running metabolic equationsTexas Tech University, Kinesiology and Sport ManagementACSM Health Fitness Instructor workshop, metabolic calculations (sample problems)Opened 19 September 2026Sets out both equations and works examples with them. Walking: VO2 = speed x 0.1 + grade x speed x 1.8 + 3.5, speed in m/min, grade as a fraction. Running uses 0.2 and 0.9. Our implementation reproduces the document’s own two worked examples exactly, 17.44 ml/kg/min at 2.5 mph and 6%, and 44.6 at 6.5 mph and 4%, which is how we checked it. GRADED D, NOT B, DELIBERATELY: the site’s B means corroborated across two or more independent sources, and this is one teaching document. We looked for a second open source stating the same coefficients and did not find one in the time we gave it, so the grade says what is true, that we took it as published and did not verify it against a second.
- Not established
- The speeds the ACSM equations are valid overNo primary source we could openThe figures are commonly quoted as about 1.9 to 3.7 mph for walking and above 5 mph for runningThe equations are sourced; their valid range is not. The figures above trace to a certification-prep site that attributes them to "ACSM’s Guidelines for Exercise Testing and Prescription" without naming an edition or page, and we could not open a primary statement of them. So the incline calculation here applies the WALKING equation only, stops at the top of that commonly quoted band, and says so rather than extrapolating past a boundary nobody has shown us.
- Independently verified, Independent publication
- One mile is exactly 1.609344 kmNIST (US National Institute of Standards and Technology)SI units — lengthOpened 19 September 2026Corroborated byWeights and Measures Act 1985 (UK)Schedule 1, Part VI: Mile = 1760 yards; YARD = 0.9144 metreOpened 19 September 2026NIST states that the inch has been exactly 25.4 mm since the international yard and pound agreement of 1959. A mile is 63,360 inches, so it is exactly 1,609.344 m. UK statute gives the same number by a different route: Schedule 1 Part VI of the Weights and Measures Act 1985 sets "Mile = 1760 yards" and "YARD = 0.9144 metre", and 1760 x 0.9144 is 1,609.344 exactly. THE CAVEAT, because it is the reason this is a B and not higher: both descend from the same 1959 international agreement, so they are independent publications rather than independent measurements. Neither copies the other, and an error in one would not reach the other, which is what the B test asks. It is a definition rather than a measurement either way, which is why every conversion on these pages is exact.
Limits
Every figure assumes the belt holds 12% and 3 mph for the whole 30 minutes, with no warm-up and no easing off. A machine out of calibration will not be doing what the console says, and we have not measured any machine's belt speed or incline.
We make no claim about what this workout does for anyone, and we do not repeat the story of where it came from, because we could not source either. What the page can tell you is what the settings work out to, and which of the machines we hold records for can reach them.
Related tools
Looking for a machine rather than a number? See our guide to treadmill workouts built around pace and incline. Every specification there carries its source and the date it was checked.