The 12-3-30 Treadmill Workout: A Complete UK Guide

What Is the 12-3-30 Workout?

The 12-3-30 method is a treadmill workout created by American content creator Lauren Giraldo back in 2019. The concept is straightforward: set your treadmill to a 12% incline, walk at 3 miles per hour, and keep going for 30 minutes. That is where the name comes from in case you hadn’t guessed!

Giraldo shared the routine on social media claiming it helped her lose 30 pounds, and the video has since racked up over 14 million views. What started as one person’s gym habit has become one of the most popular treadmill workouts in the world, and it shows no signs of slowing down.

The appeal is obvious. There is no complicated programming, no intervals to remember, and no running whatsoever. You set the machine, start walking, and that is your session done. For anyone who finds the treadmill monotonous or dreads the idea of running, the 12-3-30 offers a genuinely challenging cardio workout without the impact. 

It’s also slow enough to be able to do comfortably while you watch a show, or even work while you’re doing it if you have an under desk treadmill with incline. 

The 12-3-30 in Kilometres: UK Settings

If you are attempting the 12-3-30 in the UK, most gym treadmills and many home treadmills display speed in kilometres per hour rather than miles per hour, as we’re closer to the European market than the US market where they also still work in miles. Don’t despair though, 3 mph equals 4.8 km/h.

So the UK version of the workout is: 12% incline, 4.8 km/h, 30 minutes. Doesn’t roll off the tongue as nicely as 12-3-30, but unless you’ve set your treadmill to show units in miles, that’s how it’s going to look! 

Some people round this to 5 km/h for simplicity, which bumps the intensity up slightly but keeps you in the same ballpark. Either setting works perfectly well. If you want an exact calculator of effort, intensity levels, and the conversion from km/h to mph or vice versa, check out our treadmill speed calculator.

As for the incline, a 12% grade is the same regardless of whether your treadmill uses metric or imperial units. Just dial in 12 and you are sorted.

One thing worth noting: not every treadmill goes up to 12% incline. Many budget models and walking pads top out at around 5% to 8%. If your machine does not reach 12%, go as high as it allows and increase the speed slightly to compensate.

A 10% incline at 3.42 mph (5.5 km/h) will give you a similar level of effort. But if you’re set on keeping the exact workout parameters, check out these home treadmills with incline.

How to Do the 12-3-30 Workout Step by Step

The beauty of this workout is its simplicity. Here is how to get started:

Warm up first. Spend three to five minutes walking on a flat surface or a gentle 2% to 3% incline at around 4 km/h. This gets blood flowing to your legs and prepares your calves and Achilles tendons for the steeper gradient ahead. Jumping straight onto a 12% incline from cold is a recipe for soreness and delayed onset muscle soreness.

Set your incline to 12% and your speed to 4.8 km/h (or 3 mph if your treadmill uses imperial). Start walking. The first five minutes will feel manageable. By minute ten, you will notice your heart rate climbing. By minute twenty, your glutes and hamstrings will be working hard.

Maintain good posture. Stand upright rather than leaning forward into the incline. Keep your core engaged and resist the urge to grip the handrails, as holding on significantly reduces the workload and changes your natural gait. If you need to hold on for balance, rest your fingertips lightly on the side rails rather than gripping with both hands.

Cool down. After 30 minutes, gradually reduce the incline to flat and slow your pace to around 3.5 km/h for three to five minutes. This helps bring your heart rate back down steadily and reduces post-workout dizziness.

What Does the 12-3-30 Actually Do to Your Body?

Walking on a steep incline is not the same as strolling through the park. Here is what happens physiologically when you do the 12-3-30.

Cardiovascular Fitness

Walking at a 12% incline elevates your heart rate into the moderate-intensity zone for most people. According to the NHS physical activity guidelines, adults need at least 150 minutes of moderate-intensity activity per week. Doing the 12-3-30 five times a week gets you to exactly that threshold. Even three sessions a week delivers 90 minutes, which is a meaningful contribution to your cardiovascular health.

Research from the British Heart Foundation confirms that regular brisk walking reduces the risk of developing heart and circulatory diseases, and just 11 minutes a day of moderate physical activity is enough to lower the risk of an early death.

Lower Body Strength

A steep incline forces your glutes, hamstrings, calves, and quadriceps to work significantly harder than flat walking. You are essentially walking uphill for half an hour, which builds muscular endurance in the posterior chain over time. Think of it as somewhere between a flat walk and a weighted lunge, repeated for thousands of steps.

Research published in the Journal of Gait and Posture has shown that incline walking increases activation of the lower-limb muscles compared to walking on a level surface, particularly in the quadriceps and hamstrings. This makes the 12-3-30 a surprisingly effective lower body workout without any weights at all.

Calorie Burn

This is the question everyone asks. How many calories does the 12-3-30 burn?

The honest answer is that it depends on your body weight, age, fitness level, and metabolism. As a rough guide, most people burn somewhere between 150 and 300 calories during a 30-minute session. A heavier person will burn more, a lighter person will burn less. That said, incline walking burns substantially more than flat walking at the same speed. One study found that walking at a 10% grade increased calorie expenditure by approximately 113% compared to flat walking at a similar pace.

A peer-reviewed study published in the Journal of Exercise Science and Fitness compared the 12-3-30 workout directly against self-paced treadmill running. The researchers found that while running burned calories faster (roughly 13 kcal per minute versus 10 kcal per minute for the 12-3-30), the incline walking workout used a greater proportion of fat as fuel. Around 41% of energy came from fat during the 12-3-30, compared to 33% during running. So while running is more time-efficient for raw calorie burn, the 12-3-30 may have an edge when it comes to fat oxidation specifically.

Joint-Friendly Cardio

One of the biggest advantages of the 12-3-30 over running is the reduced impact on your joints. Walking, even on a steep incline, puts far less stress on the knees, ankles, and hips than running does. A 2014 study published in Gait and Posture found that walking at a steep incline actually decreased peak knee joint loading compared to level walking. For anyone dealing with joint issues, recovering from injury, or simply wanting a cardio option that will not leave them hobbling the next morning, this is a significant benefit.

If you are interested in building up to running eventually, the 12-3-30 can serve as an excellent foundation. It builds cardiovascular fitness and leg strength without the impact, which is similar in principle to how programmes like Couch to 5K gradually increase running demands over time.

Mental Health Benefits

The mental health benefits of regular walking are well documented. The NHS notes that walking can reduce stress, improve mood, and contribute to better sleep quality. The 12-3-30 fits neatly into this picture, offering a structured 30-minute session that many people find meditative once they get into a rhythm. Put on a podcast, queue up a playlist, and the half hour flies by.

12-3-30 Workout Results: What to Expect

Let us be realistic about what the 12-3-30 can and cannot do.

In the first two weeks, expect the workout to feel genuinely difficult if you are not already active. Your calves and glutes will be sore after the first few sessions, and you might not manage the full 30 minutes at 12% straight away. That is completely normal. Start at an incline you can sustain and work your way up.

After a month, you should notice improved stamina. The sessions that once had you gripping the handrails will feel more manageable. Your legs will feel stronger, and you will likely notice improvements in your overall energy levels throughout the day.

After three months of consistent sessions (three to five times per week), most people report noticeable changes in body composition, improved cardiovascular fitness, and better endurance in other activities. Some people report visible changes in their glutes and legs from the consistent incline work.

As for weight loss specifically, the 12-3-30 alone is unlikely to produce dramatic results without dietary changes. Losing weight on a treadmill comes down to sustaining a calorie deficit over time. The 12-3-30 contributes to that deficit, but what you eat matters just as much, if not more. The workout is one piece of the puzzle, not a magic solution.

Who Is the 12-3-30 Best Suited For?

The 12-3-30 is not for everyone, but it suits a wide range of people.

Beginners who want a structured routine that does not involve running will find this approachable and repeatable. The simplicity of the programme means there is nothing to overthink. You just turn up and walk.

People who dislike running but still want an effective cardio workout will appreciate that the 12-3-30 delivers genuine cardiovascular benefits without a single stride of running.

People with joint concerns who need lower-impact alternatives to running or HIIT will find the 12-3-30 far gentler on their knees and ankles while still delivering a meaningful workout.

Experienced exercisers who want an active recovery day or a change of pace from their usual training can slot the 12-3-30 in as lighter cardio alongside their resistance training.

That said, if you are already very fit and your resting heart rate is low, the 12-3-30 might not push you hard enough to count as moderate-intensity cardio. In that case, you would benefit from increasing the speed, the incline, or both. A 15% incline at 5.5 km/h is a different beast entirely.

Common Mistakes to Avoid

Holding the handrails. This is by far the most common mistake. Gripping the rails takes a significant amount of load off your legs and core, effectively turning a challenging incline walk into something much easier. If you cannot walk at 12% without holding on, drop the incline to a level where you can walk hands-free and build up gradually.

Skipping the warm-up. Walking straight onto a 12% incline from standing is asking for tight calves and sore Achilles tendons. Always warm up on a flat or gentle incline for a few minutes first.

Doing it every single day. Your muscles need time to recover, especially when you are starting out. Three to five sessions per week with rest days in between is far more sustainable and effective than seven days straight. Overuse injuries from repetitive incline walking can affect the lower back, calves, and Achilles.

Leaning forward excessively. On a steep incline, it is natural to lean slightly forward, but hunching over or bending at the waist shifts the effort away from your glutes and puts strain on your lower back. Stand tall, keep your chest open, and let your legs do the work.

Expecting overnight transformations. Social media is full of dramatic before-and-after content, but real results from the 12-3-30 come with weeks and months of consistency. If you are doing it primarily for weight management, pay attention to your diet as well. Exercise alone rarely produces the transformations that social media suggests.

How Many Steps Is the 12-3-30?

At 4.8 km/h (3 mph) for 30 minutes, you will cover approximately 2.4 kilometres, or about 1.5 miles. In terms of step count, most people rack up somewhere between 3,000 and 4,000 steps during a 12-3-30 session, depending on stride length.

According to the British Heart Foundation, research shows that as few as 3,867 steps per day reduces the risk of dying from any cause, and every extra 1,000 steps is linked with a further 15% reduction. A single 12-3-30 session essentially gets you to that baseline in half an hour, before you have done any other walking that day.

How Often Should You Do the 12-3-30?

The creator of the workout suggests five times per week, which conveniently hits the NHS-recommended 150 minutes of moderate activity. However, this is a target to work towards, not a starting point.

If you are new to exercise, begin with two to three sessions per week and see how your body responds. Pay attention to any soreness in your calves, Achilles, or lower back. Increase frequency gradually once you are confident your body is recovering well between sessions.

For more experienced exercisers, the 12-3-30 works well as one component of a broader training programme. Use it on your cardio days and complement it with strength training on other days. A well-rounded fitness routine, as the NHS recommends, includes both aerobic activity and muscle-strengthening exercises on at least two days per week.

Do You Need a Specific Treadmill for the 12-3-30?

You need a treadmill that can reach a 12% incline and sustain a speed of at least 4.8 km/h. Most mid-range and higher-end treadmills handle this easily. Many folding treadmills in the £400 to £800 price range offer inclines up to 12% or 15% and are perfectly suited to this workout. Check out our full guide on home treadmills with inclines of 12% for more information.

Where you might run into trouble is with walking pads and very basic budget treadmills. These typically have limited or no incline adjustment. If the 12-3-30 is specifically why you are buying a treadmill, make sure the model you are looking at hits 12% incline before you commit.

Modifications and Progressions

The 12-3-30 does not have to stay static forever. Here are some ways to adjust it depending on your fitness level.

If 12% is too hard right now: Start at 6% to 8% incline and keep the speed at 4.8 km/h. Add 1% to the incline each week until you reach 12%. There is no shame in building up gradually, and you will still get a solid workout at lower inclines.

If it is becoming too easy: Increase the speed to 5.5 or 6 km/h, bump the incline to 14% or 15%, or extend the duration to 40 or 45 minutes. You could also try interval variations, alternating between 12% and 15% incline every five minutes.

If you want more variety: Alternate the 12-3-30 with other treadmill workouts. Use it on some days and try a flat-surface interval session on others. Mixing up your training prevents boredom and reduces the risk of overuse injuries from doing the same movement pattern every session.

Frequently Asked Questions

Is the 12-3-30 workout effective for weight loss?

It can contribute to weight loss as part of a calorie deficit, but it is not a guaranteed fat-loss solution on its own. The workout burns roughly 150 to 300 calories per session depending on your body weight. Combined with a sensible diet, consistent 12-3-30 sessions can absolutely support gradual, sustainable weight loss. But the workout alone, without any dietary changes, is unlikely to produce dramatic results.

Does the 12-3-30 work for building muscle?

It will build some muscular endurance in the glutes, hamstrings, and calves over time, particularly if you are new to exercise. However, it is not a substitute for dedicated resistance training. Think of it as a lower body endurance workout with cardiovascular benefits rather than a muscle-building programme.

Is the 12-3-30 bad for your knees?

For most people, no. Walking on an incline is lower impact than running and some research suggests it actually reduces peak knee loading compared to flat walking. However, if you have existing knee issues, it is worth starting at a lower incline and increasing gradually. If you experience pain, stop and consult a physiotherapist before continuing.

Can I do the 12-3-30 every day?

It is not recommended, especially when starting out. Your calves, Achilles tendons, and lower back need time to recover from the sustained incline work. Three to five sessions per week with rest days in between is a more sensible approach. Doing it daily increases your risk of overuse injuries.

What is the 12-3-30 equivalent on a treadmill that does not reach 12% incline?

If your treadmill maxes out at 10%, increase the speed to around 5.5 km/h to compensate for the reduced incline. The goal is to maintain a heart rate in the moderate-intensity zone, where you can talk but would struggle to sing. Adjust the settings until you find that sweet spot on your particular machine.

How does the 12-3-30 compare to running?

Running burns more calories per minute but is higher impact. The 12-3-30 burns a higher proportion of fat as fuel and is far gentler on the joints. For most people who are not training for a race, the 12-3-30 offers an excellent balance of challenge and sustainability. If you enjoy it and stick with it, it is going to serve you far better than a running programme you abandon after two weeks.

The Bottom Line

The 12-3-30 treadmill workout is not a fad. It is a simple, evidence-backed incline walking routine that delivers genuine cardiovascular and lower body benefits for a wide range of fitness levels. It is not magic, and it is not going to replace a comprehensive training programme, but as a standalone cardio workout or as part of a broader routine, it is one of the most accessible and effective things you can do on a treadmill.

Set the incline, set the speed, walk for half an hour. That is it. No gimmicks, no complicated programming. Just consistent effort over time. And if the social media results are anything to go by, a lot of people are finding that is more than enough.