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How to Calculate Total Amps in a Breaker Panel? – Only 4 Steps

Written by Edwin Jones / Fact checked by Andrew Wright

how to calculate total amps in a breaker panel

Isn’t it scary and overwhelming to power up your home without knowing the amperage consumed? It’s unlikely that you continuously use your electricity to the max every day. However, when you don’t know how to calculate total amps in a breaker panel, chances are you may encounter electrical, or worse, fire hazards.

To find the amp capacity of your breakers inside the panel box itself, you can use the Power formula (I=P÷V). Our goal here is to get the amps in your breaker panel before adding more circuit branches.


Steps to Calculate Your Breaker Panel’s Total Amps


What You Will Need

Electrical panel load calculation is a minor electrical project that doesn’t necessarily require a professional contractor, so don’t worry much about complicated tools because you’ll only need three things:

  • Calculator

Since you’re going to solve the total amps of your panel, a total amperage calculator is a big help. Although you can crunch the numbers yourself, a digital or scientific calculator can make computations easier.

If you have an electrical code calculator, you may use it. However, since we’re doing simple equations, which only involve adding, multiplying, and dividing, a simple but accurate calculator will fit the job.

  • Pen and paper

You are required to write down the rated amperages of your circuit breakers, so you should have a pen and paper. Using a whiteboard will work as well. Jutting down the important numbers when you calculate amps in a circuit is beneficial when we purchase materials for the new circuit system.

Also, these written notes will serve as a basis for future load calculations. Sometimes, when there’s a breaker panel inspection, you can also show this to your contractors and refer to it if there are any anomalies.

  • Flashlight

Main breaker panels are not usually placed in well-lit areas. Contractors hide them inside your basement, attic, or any room which is not frequented by people.

Use a flashlight to check amps on a circuit breaker. Circuit breakers have their amps written on them in small fonts, and reading it in a dark area can potentially result in a misreading.

A lamp, headlight, or handheld flashlight is good. What’s important here is that you’ll have a good vision of your CB amp ratings when you write them on paper. A single mistake will result in an inaccurate calculation, so make sure to view your breaker panel with proper lighting.

  • Protective Equipment (Gloves and Boots)


The listed tools you’re going to use are accessible and commonly found in most homes. Now, learn how to tell how many amps your electrical panel is supplying by following these easy steps.

What we’re trying to achieve here is to get the hypothetical amount of the total amps of the sub breakers installed in your panel.

This step is necessary to get the correct amperage rating for your panel. At the end of this tutorial, you’ll know if you’ll need a panel upgrade or if it’s spacious enough for a new circuit branch.

Step 1. Open the cover of your breaker panel

Before everything else, for you to be able to inspect all of the circuit breakers installed in your load center, open the breaker panel door or the cover itself. This step is the most dangerous part of the process. Please note that the surface of and around the breaker panel is an electric-prone area. Use insulated gloves and boots for your protection.

There’s no rocket science behind opening a breaker panel cover. What you need to remember is when you unscrew the lid, start from the bottom, going all the way to the top. And as you reach the last two screws, hold the cover in place until you’re ready to pull it out.

Step 2. Determine every circuit breaker’s amp rating

Once you’ve revealed all the circuit breakers, use your flashlight to check each installed breaker—single-pole or multi-pole. Remember that we need to exclude the Main circuit breaker in totaling the amps of the breaker panel; you can find this breaker either at the top or bottom.

Now, write each amp rating of your circuit breaker on a piece of paper. Note that a multi-pole breaker has the same ampacity for each leg. For example, a 15-amp double-pole breaker has 7.5 amps for each leg and not 15-amps.

Step 3. Add them all and get the load limit of the circuit breakers

Next, add up all of the circuit breakers’ amps, then multiply it by the load limit requirement, which is 80%. To determine electrical panel amperage easily, let me give you a sample problem as a basis:

For instance, a house has one 15-amp breaker for light fixtures, two 20-amp breakers for bedrooms, one 30-amp breaker dedicated to a water heater, and another 20-amp breaker for the garage. In total, this home has 105 amps.

However, considering the load limit, which requires a homeowner to use only 80% of the total load, the actual limit of the circuit breakers is 84-amps. (15+20+20+30+20= 105A, multiplied by 80% = 84A)

Step 4. Get the amperage for the electric panel

Now that you’ve got the total amps in your breaker panel, you can determine the best size for the main panel. The panel’s rating should be at least as high as the amps you use. Your panel should have a label that notes its amperage.


And that’s a wrap! I hope you’ve learned how to calculate total amps in a breaker panel with the example I gave you. Keep in mind that you’ll need to follow the 80% load limit for every load computations. This safety regulation is the best way to avoid electrical accidents.

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