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How To Calculate Excavator Bucket Capacity?

Nov 26 , 2022

The bucket acts as the business end of the excavator. Choosing the right size and type of excavator bucket for your application and the material you are digging or moving can increase production without overstressing your equipment.

Use this guide to learn how to size an excavator bucket and how to calculate excavator bucket capacity.

Excavator bucket size

Size is the primary consideration when choosing a bucket. If you are digging a trench, the width of the trench will determine the width of the bucket you need. If you are digging foundations or backfilling excavations, the larger the bucket size, the better, within the recommended range of bucket sizes for excavators. The range of bucket sizes available for a particular excavator is determined by the size of the excavator. This is also true for mini excavator bucket sizes.

A larger bucket can increase productivity as you can move more material in one cycle.

Rock Bucket

 Rock Bucket

How to calculate excavator bucket capacity?

The bucket capacity of an excavator varies according to many factors, including material density, fill factor and production rate. A bucket suitable for gravel may not be suitable for loose soil.

To calculate the bucket capacity of an excavator, follow these steps.

Use a reputable source to determine the standard weight of any material you need to lift. Each bucket comes with a fill factor table that lists the various materials. These values will tell you how much of a particular material the bucket can handle based on the material density.

Rock Bucket

Rock Bucket

Next, time the digging operation of the excavator. It starts when the bucket starts digging and stops when it starts digging for the next load. Divide this number by 60 to find the excavator's cycle time.

Use the cycle time to determine the production rate per hour. Divide the target weight per hour of loaded material by the cycle time. For example, if you have to move 500 tonnes per hour and the cycle rate is 120 cycles per hour, you must move 500/120 = 4.17 tonnes per cycle.

Divide the cycle payload amount by the material density found in step 1. This will give you the nominal capacity of the drum.

Finally, divide the nominal capacity by the fill factor of the material to obtain the required capacity of any material required for each drum.

Brands will usually provide a chart showing the capacity of the drum based on the size and material of the drum.

Rock Bucket

 Rock Bucket

Calculating the lift ratio

To ensure that the excavator has enough power to lift the bucket you are going to use filled with the material you need to lift, do some mathematical calculations.

  • Note the bucket capacity, listed in cubic yards.

  • Multiply it by the material density of the heaviest material you plan to lift. (Consult the manufacturer's material density table or any standard reference.)

  • Add the weight of any attachments to obtain the lifting weight. (Remember that the bucket weight may or may not be included in the lifting capacity; if it is, do not add it here.)

  • Take the lifting weight and divide it by the adjusted lifting capacity, i.e. the maximum lifting capacity plus the bucket weight. The result is the lift ratio.

  • If the lift ratio is less than 1, the bucket will work for the material you want to lift. If it is higher than 1, the bucket is too heavy for the excavator. You need a smaller bucket - or a bigger excavator.

If you are working with dense material and you need to extend the machine as far as possible, a smaller bucket is safer, even if you have hired the right size excavator. Filling the bucket with heavy material and extending the bucket bar to the end of its working range can cause the machine to tip over.

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