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How To Measure For Rain Gutters The Easy Way (Step-by-Step)

how to measure rain gutters

How To Measure For Rain Gutters and Downspouts

Rain gutters are the unsung heroes of your house. They protect your home, and more importantly, they protect you from nature’s wrath. Rain gutters are necessary to protect the exterior of your home, but they can be tricky to measure for. The last thing you want is to order the wrong amount, only to be left short.

If you’re contemplating replacing your gutters yourself it will be important to get accurate measurements to calculate the total length of gutters you will need to purchase.

Included below are a series of steps that you can follow that will provide you with accurate measurements. These steps are designed to make this task as easy as possible, saving you time and money in the process.

Tools You’ll Need To Measure Rain Gutters And Downspouts

In order to keep things simple and quick, you should start by gathering all the tools that you’ill need in order to get the job done in one shot. This will allow you to work without having to stop in order to search or go shopping for something you need. Which I know from experience, to be a frustrating waste of time.


You’ll need direct access to the gutters, so a ladder is going to be a critical tool to have on hand. Make sure that the ladder provides you access to the top of the existing gutters, or even better, the roof itself. You’ll need a six-foot ladder at minimum, but it would be ideal to get one that is at least eight feet in height to provide you with a more stable platform to work from.

I use the Little Giant foldable ladder around my house. It’s perfect for accessing the roof as well as folding down for the smaller indoor projects.

Tape Measure

A tape measure is necessary in order to determine lengths accurately. If you can find one that is at least sixteen feet in length you will be able to calculate the measurements with a minimal amount of work. If you can get a hold of a 25ft tape measure, that’d be even better.


To keep things moving along quickly, I would suggest grabbing some twine as well. You can use the twin to make the actual measurements instead of the tape measure. The twine will be easier to fasten down and will allow you to measure the length on the ground, which is often quicker as well as safer to do.

Pen and Paper

Make sure that you have a pen or pencil along with some paper. This will allow you to write down your measurements without having to memorize your calculations as you go along. Trust me, there is nothing more frustrating than having to measure the gutter runs a second time.


Finally, make sure to grab some tape. This will allow you to fasten the twin along the gutter on one end and mark the other end of a run. Avoid using scotch tape and select something with more adhesive power to keep things secure as you work.

Determining The Safest Approach

Before you begin the job, it will be important that you determine how you can reach the gutter system for quick measurements safely. One point of access will be from the ladder itself. This would be the safest approach if you have a steep roof or a home with gutters that are easily accessible from the ladder.

Another access point would be from the roof itself. If the roof is flat enough to safely work from, or the gutters are harder to access from the ladder, you might contemplate measuring from it instead of the ladder. Once you determine how you access the gutter system you can begin measuring the runs.

Measuring The Gutter Runs From A Ladder

Safely Set The Ladder

Select an end to start from. Place your ladder in an area that provides it with stability at the base and the top so that it will not move as you stand on it. Put the twin and tape in a pocket or pouch so that your hands are free as you climb up the ladder rungs or steps.

Brace Yourself Against The Gutters

Move up the ladder one step at a time to the point that you need to reach the top of the gutter system comfortably. Make sure to brace yourself using your lower torso and legs so that you can free your hands to work. If it is more comfortable or safe to work from below the gutter system, you can make the measurements along the bottom.

Secure Twine With Tape

Use the tape to secure the end of the twine at one end of the run. To keep measurements as accurate as possible, do not leave a tag end on the twine or bundle the end when you tape it down. Allow the twine to fall towards the ground and climb down the ladder, making sure to use your hands for stability as you move.

Move Ladder To Other End of Run

Once you are down, move the ladder to the other end of the run you are measuring. Set the ladder up again and bring the twine to the ladder. Climb up the ladder with the twine in your hand and support yourself as you did previously. You can then stretch the twine to the end of the run and mark the point with another piece of tape.

Measure Twine Safely On The Ground

Allow the twine to fall to the ground and climb down the ladder. Once you are down you can tug on the twine to pull it away from the secured position.

You can now use a tape measure to determine the length of twine, writing down these calculations on your paper. Repeat these steps for all runs where your gutters will be placed.

Measuring Gutter Runs From A Roof

Safely Access The Roof

Locate the easiest point to access your roof. Keep in mind that some homes will provide roof access from a window on an upper level. In this case, you might be able to avoid using a ladder to measure the runs.

If you are using a ladder, climb up the rungs one at a time. You will want to bring your measuring tape, twine, tape, and writing supplies with you. Keep safety in mind as you climb onto the roof from the ladder.

Secure Twine On One End Of Run

Once you are safely on the roof, move carefully to one end of the gutter run. Secure the end of the twine to the gutter edge with your tape as described above. You can move along the roof, bringing the twine to the other end of the gutter run.

Measure Length Of Twine

Mark the measurement with a piece of tape and then pull the twine off of the other end of the gutter. Use your tape measure to determine the length of the twine, marking down this calculation.

How To Measure Downspouts

You can use the same method to calculate the downspouts on your gutter system. Using a ladder will save you time with these measurements. The twine can be taped to bends and elbows as you move down towards the ground to provide you with an idea of the extra length needed at these points.

How Many Downspouts Do You Need For Rain Gutters?

Downspouts are the best way to divert rainwater away from your house, preventing it from flowing all over your yard and into your foundation, but you need to have enough of them if you want it to do its job effectively.

The general rule of thumb is one downspout per 20 feet of guttering, but more may be necessary depending on how much water they will be dealing with or whether or not they are designed according to local weather patterns.

Adding It All Up

After all of your measurements are made, you can add up the totals to give you an idea of the amount of gutter you’ll need to purchase. Make sure to add a little extra to your total to cover potential errors. Depending on the difficulty of the project, I’ll add about 10% to 15% extra when I make my order. It could save you an extra trip later and prevent unnecessary delays in completing the project.

how to measure gutters step by step

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