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Ladder Height Chart & Calculator For Safe Operation

Working with a ladder is naturally a little risky. You’re relying on the ladder to get you where you need to go, without collapsing or twisting under you. Having a ladder that’s the right height isn’t about simple convenience, it’s also incredibly important for your safety.

In this article, we’ll cover how you find the right height ladder for your project, some tips to help keep you safer on the job, and other safety details.

Ladder Height Chart

Step Ladder Height Chart

Ladder HeightMaximum Reach*
4 Feet8 Feet
6 Feet10 Feet
7 Feet11 Feet
8 Feet12 Feet
10 Feet14 Feet
12 Feet16 Feet
14 Feet18 Feet
16 Feet20 Feet
*Assumes a person of average height (5′ 5″)

Extension Ladder Height Chart

Ladder HeightMaximum Reach*Height to Top Point**
16 Feet15 Feet9 Feet Maximum
20 Feet19 Feet9 Feet to 13 Feet
24 Feet23 Feet13 Feet to 17 Feet
28 Feet27 Feet17 Feet to 21 Feet
32 Feet31 Feet21 Feet to 25 Feet
36 Feet34 Feet25 Feet to 28 Feet
40 Feet37 Feet28 Feet to 31 Feet
*Assumes a person of average height (5′ 5″)
**Top point reflects section overlap,

How to Calculate the Ladder Height Needed

Getting the right height for your ladder is critical for success and safety in any project. But, every project’s needs are a little different. You also need to remember the angle of the ladder, and that you can’t stand on the absolute top rung of any ladder safely.

It’s important to know how to calculate the necessary height for different kinds of ladders, so we’re going to look at step ladders and extension ladders separately. The main difference between these two ladder styles is height, so you can apply the same rules to other styles of ladders in the same height category as well.

Step ladders

Step Ladders are any ladder that’s 20ft or shorter, not just your kitchen step ladder or the one you use for the highest shelves in your garage.

First, you need to know the height of your work area before you can find out whether a step ladder will work for you. Generally, any work height up to about 23 ft will work with a step ladder.

The working height you need is the combined height of the ladder (on a safe rung) and the height of the person using it. Most people are tall enough that you can subtract about 4ft from the height of your work surface to calculate the size of ladder you need.

So if you’re working on a surface 10ft high, you need a ladder at least 6ft tall. If your work surface is 13ft high, you’ll need a ladder that’s 9ft tall.

Technically you can push a step ladder to reach spaces up to 24ft tall with this formula, but we generally don’t recommend it because you’ll probably need to be higher on the ladder without putting yourself at risk of falling.

Extension Ladders

Extension ladders are similar to step ladders, but you need to take more factors into account when you’re planning for ladder height. Since extension ladders are taller than 10ft you’ll end up losing more height to the angle of the ladder than you lose with a step ladder.

It’s also important to make sure the ladder is secure and stable, which means you’ll likely need some extra height. For instance, you need three feet of ladder overhang to safely climb from a ladder onto a roof without overbalancing the ladder.

Even if you’re planning to lean the ladder against your work surface or some scaffolding and don’t need to climb off at the top, you’ll still want a couple of extra feet so you can brace more effectively against the ladder.

A good rule of thumb is 3ft extra length for any project. So start with the height of your work area, plus the extra length for safety. If you need to access something 15ft off the ground, that means you need an 18ft ladder so far.

You aren’t done yet.

Now you need to calculate the extra height needed for a safe angle. You’ll need an extra 1ft of height for every 4ft up you need to go. That extra foot will let you set up the ladder’s legs further away, to maintain a safe and stable angle.

For demonstration, let’s say you’re working on something 16ft off the ground. 16 divided by 4 is 4. So you’ll need a ladder that is 16 (the height of the project) + 4 (the extra length for a safe angle) + 3 (ladder overhang for stability) = 23ft.

Simplified, let’s say the height of your project is x, angle height is (x/4), plus the overhang is 3. So your extension ladder height calculation is:

X + (X / 4) + 3 = Height Required

In general, if you can’t get a ladder that’s the exact height you need it’s better to go with a ladder that’s slightly longer instead of a shorter ladder. However, longer does not always mean safer. Try to stay within 1-3ft of the length you need.

If you do a lot of work on ladders and need a lot of different heights, it’s worth investing a little more to get a ladder with more adjustment options. That way you’ll always be able to meet your height requirements up to the tallest safe extension on your ladder.

Types Of Ladders And Their Uses

Now that you know how to get the right height for your ladder, you’re probably wondering what style of ladder is best for your project.

Most professional contractors will end up with several different ladders that they use for different situations, and it’s important to know which version is going to be the safest and most effective in any situation.

Each ladder is a little different, but we’ll take a closer look at each type so you can better match your ladders to your needs.

Step ladders

Step Ladders are defined as any ladder 20ft long or shorter. Ladders that are 4ft long or shorter are considered step stools, not step ladders.

Notice that we said ‘long’, not ‘tall’ the truth is that most step ladders will not stand 20ft tall when they are set up properly because they aren’t vertical. The measurement is taken along the legs of the ladder, but standing height can vary quite a bit from style to style and depending on how the ladder is set up.

Step Ladders are also a fixed height, they can’t be shortened or lengthened, otherwise, they would be considered an extension ladder.

Beyond that though, there aren’t many style limitations. A step ladder could be a standard ladder, an A-frame ladder, or any other stable design that doesn’t change length once it’s set up. Even the folding step ladder you use to reach the highest parts of your garage counts, assuming it’s more than 4ft long!

Step ladders are generally considered the most stable and durable option because there are fewer failure points in their design compared to other ladders. A-frame step ladders are usually the most commonly accepted as step ladders in part because of their extreme stability and durability compared with other styles.

While these ladders are highly stable, they are only considered safe when they are placed on solid ground or flooring. These ladders should never be used stacked on top of furniture, unstable platforms, or scaffolding.

Extension Ladders

Extension ladders are another incredibly common design and are popular for reaching things that step ladders can’t. Extension ladders aren’t self-supporting though, so they aren’t quite as stable. They also aren’t always longer than step ladders either!

However, extension ladders are usually easier to store than step ladders since they only have 2 legs instead of 4 like an A-frame step ladder. That can make them more popular as portable ladders, as well as your main ladder for smaller spaces and smaller storage areas.

Extension ladders can have anywhere between 1-3 sections that expand and can have a fairly wide range of extension options. Some can only extend an extra couple of feet from their normal height, while others will add considerable length when you use every extension option.

It is important to look at how your ladder expands though. Some ladders will let you make tiny by-the-inch adjustments, while others expand a foot or more at a time. Knowing how much your ladder will extend will help with your height calculations since it will let you get closer to your ideal height.

Telescoping Ladders

Telescoping ladders are similar to extension ladders in that you can adjust the height of the ladder, but they collapse a lot smaller than your average extension ladder. Telescoping ladders also are often more adjustable than extension ladders since you can control exactly how much length you want to extend.

However, telescoping ladders don’t tend to get as long as extension ladders. The upper limit is usually around 15-17ft, though new innovations and designs may allow them to get a little longer in the future.

That’s in part because telescoping ladders are inherently less stable than step ladders and extension ladders. After all, there are a lot more connections and possible points of failure on these ladders.

They’re great for when you need a moderately tall ladder and need to be able to travel between different locations with a smaller vehicle or little storage space, but they aren’t as stable or reliable as a step ladder or extension ladder of the same height.

That said, telescoping ladders still have to meet strict safety requirements, so a well-maintained telescoping ladder is still an absolutely safe option.

Multiposition Ladders

Multiposition ladders are the swiss army knife of the ladder world. They typically work as a flat ladder like an extension ladder, as an A-frame ladder, and often as a 90-degree ladder as well. These ladders can often act as a kind of scaffolding, and many fold in several locations so you can create a custom shape and support system to meet the needs of a non-standard workspace.

These ladders are great anytime you need a ladder that does a little more, but they aren’t necessarily the best option out the gate.

That’s because multiposition ladders, like telescoping ladders, have more points of failure. All those joints and locking mechanisms have to be able to handle a lot of wear and stress over time, which means that multiposition ladders usually have a slightly shorter lifespan than less complicated ladders.

They also often need more care and maintenance since the joints frequently need lubrication and need to be kept dry to prevent rusting and corrosion.

Safety Tips for Ladder Height

Reach No More than 4 Ft From Your Ladder

Even if you are tall enough that you can reach more than 4 ft from your ladder, it’s important not to. Reaching further can put a lot of torque on the ladder and risk twisting or overbalancing. It’s also important not to lean past the ladder when you’re reaching, even if you need to reach less than 4 ft.

Inspect and Clean Your Ladder Regularly

All ladders, especially tall ladders, need to be cleaned and inspected regularly to stay safe to use. Even a small amount of rust or corrosion can destabilize a ladder if it’s in the wrong place

Always Make Sure the Feet Are Placed Securely

Ladder feet are almost always angled to make sure you have the right angle to height ratio, but it’s important to make sure they are placed flat to the ground. The more of the foot is off the ground, the more likely you are to fall.

Too Much Height is Better than Too Little

If you don’t have a ladder that’s the perfect height for your job, it’s better to get a little extra height than to try and make a ladder that’s too short work. Up to a foot longer, you should be able to use it without any problems. Longer than that and you might have to make some adaptations.

Ideally, your ladder should be within 1-2ft of the ideal height, and it should never be more than 3. If you can’t get closer than 3ft of ideal height you should get a different ladder.

Different Load Capacity Ratings of Ladders

Of course, height shouldn’t be your only consideration when you’re looking at a ladder. You also need to consider its weight capacity.

There are 5 different load capacity ratings, from Type III to Type IAA:

  • Type IAA – 375lbs – Extra Heavy Duty
  • Type IA – 300lbs – Extra Heavy Duty
  • Type I – 250lbs – Heavy Duty
  • Type II – 225lbs – Medium Duty
  • Type III – 200lbs – Light Duty

The duty rating should be listed next to other safety notices on your ladder and should also be listed in the name of the ladder or with its description online and in-store.

Never load a ladder with more weight than it’s designed to handle, the material may buckle unexpectedly and cause an injury.


Safety should always be your primary concern when you’re working with ladders. Getting the height right might seem like a small detail, but it can be the difference between a successful project and serious injuries. The taller your ladder is, the more serious an injury it is likely to get.

Knowing how to get the right height ladders for your next project or job site is critical. Plus, working with the right ladder size, design, and weight capacity will make your job a lot easier!

Check out some of our top recommended ladders for your next project!