What Size Fuse For 1000 Watt Amp?

You should buy a 125 A fuse if you are using a Class AB amps and 90 A for a Class D amps. However, if your amp is class A then buy 250 A and again use 150 A for a class B amps. Finding the required fuse size is just a matter of mathematical calculation and amp class efficiency. 

Is your 1000 watt amps fuse just blown and you are looking for a new one? We understand how annoying it is. So what do you do now? You buy one.

But what size fuse do you buy for 1000 Watt amp?

To get into the details of the calculation, let’s get started. 

What Size Fuse For 1000 Watt Amp

The perfect fuse size for your 1000 watt amp depends on the voltage. Without any delay, let’s dive into the mathematical formula. 

The formula is Amperage = Power / Voltage

Here Power means the Watt in question. Meanwhile, the voltage rating is what the alternator supplies and it is typically within 13.8 to 14.4 V.

Now, let’s assume the voltage rating is 14.2 V and as a requirement, the rated power is 1000 W.

So, the fuse size is Fuse Amp. Size = 1000 / 14.2

                                                         = 70.422 A 

But before you go on and decide to buy a fuse with 70.42 A, you should know about the standard ampere rating in the US and Canada.

Some of the standard ratings are 

  1. 60 A
  2. 70 A
  3. 80 A
  4. 90 A

These are the available ratings in the market. After calculating, find out what fuse rating is the nearest to your mathematical value.

In the example above, we got 70.422 A. But, the closest fuse rating is 70 A. So should we go and buy 70 A? No, because this is 0.42 A less than the requirement and that means it will not be able to withstand the electric flow. More current flow means the fuse will keep blowing

So, what should we choose? 80 A No, it’s not that simple. There are different amplifier classes and each has its own efficiency. So we have to consider that too.

Classes of Amplifiers

Now you need to know about the different classes of amplifiers before diving deep into calculating the amp fuse size. 

Each of these classes differ by the efficiency of the fuse ratings. Based on its efficiency, the rated power changes.

The following table shows different classes along with their rated power


Now, we don’t blame you if your reaction is ‘What?’. But let us explain.

Let’s consider Class B amplifiers. The table above shows that it has an efficiency of 50%. What does that mean?

This simply means the initial watt input for Class B amplifiers needs to be doubled, that is 1000/0.5  = 2000 Watt. By doing this class B amplifier 50 % efficiency will get 1000 W.

Power input =  Target Power Rating / Efficiency

                         = 1000 / 0.5

                         = 2000 W

You need to find out the fuse amperes separately for each class. So, for a class B amplifier, the required fuse with a 14 V rating will be

Amperage = 2000 / 14

                 = 142.86 A

                 = 145 A

We are calculating Amperes here as fuses are always rated in amperes.

Now, let’s see the tabular value for what you might expect for 14 V and 1000 W amps.

ClassEfficiencyRated Power for 1000 (W)Calculated Value (A)Fuse Size (A)
Class A 1000 watt amps30%3333238.07250
Class B 1000 watt amps50%2000142.86150
Class AB 1000 watt amps60%1666119125
Class D 1000 watt amps80%125089.2890

Now, with the amp fuse size calculator, you can easily find the fuse size for the required amp. So, let’s consider a different rated power now.

Power = 1800 W and Voltage Rating = 14 V

Amperage = 1800 / 14

                = 128.57 A

                = 150 A

So, the fuse size for 1800 Watt Amp is 150 A.

Let’s see the amp fuse size chart for different rated power. [Assuming Voltage Rating = 14 V]

Rated Power in WattsFuse Size For Class AB (Ampere)Fuse Size For Class D (Ampere)

With that, you should be clear on how to select the right fuse size for the required rated power and voltage rating. 

Finally, we need to mention Fuse Derating. It is a technique where you derate the fuse size to avoid fuse blow. If you know how to find a fuse blow, you will know that both internal and external temperature plays a role in blowing. 

So, for 25ºC you make the fuse derate by about 25% higher. If the fuse size is 100 A, you increase it by 125 A. 

But is that it? Are we done with knowing everything about the right fuse size for 1000 watt amp? No, you have to consider the wiring gauge as well. 

What Wiring Gauge To Use For 1000 Watt Amp?

Alright, so you have bought the right fuse for your 1000 watt amps. But does that mean your work here is done? Nope. You still need to consider the wire gauge. Choose the right wire gauge for your amp.

So, what’s the correct wiring gauge for 1000 Watt amp? Let’s assume you are using class AB amps. So, the fuse size is around 125 A. The wire gauge here will be about 4 AWG (American Wire Gauge). 

But for class D amps, the fuse size is around 90 A. the wire gauge will also be about 4 AWG (American Wire Gauge). 

To avoid your fuse getting blown, it is important to buy the one with the accurate size. Now you know how to buy the most accurate fuse size for 1000 Watt Amps. 


Can I Use A Higher Amperage Fuse for a 1000 Watt Amp?

No, you should not use a higher amperage fuse for a 1000 Watt Amp. Typically, it can withstand the current flow but there is a risk of damaging the amp’s internal circuit. This is because a bigger fuse can enable more flow of current and even though nothing happens to the fuse but it’s the circuit that gets affected. 

Can I Use A Class A Amplifier instead of Class AB?

No, you should not use a Class A Amplifier instead of Class AB. Class A has only 30% efficiency compared to 60% of Class AB. That’s half the efficiency. So, the fuse requirement will be different. 

What Size Fuse For 6000 Watt Amps? 

Your fuse size should be 800 A if you are using a class AB amps. However, if your amps are class D your fuse size should be 600 A. So, make sure to know which class amp you are using before selecting the fuse size. 


Now you know what size fuse to use for 1000 Watt Amp. Hopefully, with the help of the amp fuse size calculator and the chart given, you should be able to find out the required fuse size for any watt of an amp. But make sure to keep the amplifier class and the wiring gauge in mind while you select a fuse. 

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William Baldwin

This Is William Baldwin, The Founder & Managing Editor of this website. Me and my team share automotive tips, tricks, and news

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Talha Atta

Talha Atta, a Mechanical Engineer and experienced technical content writer and editor at Autoglobes.com with a passion for the automotive industry.