How to measure the draft of a boat

Boating is most enjoyable when you know the drafting of the boat. A boat’s draft is an estimate of its length under the water. In other words, a boat draft is the minimum amount of water required to float the boat without touching the base.

When you determine a boat’s draft, you can determine the water depth to navigate. The bottom of your boat should not be damaged if its draft is near the depth of the water. Boating in water with a depth of 10 feet would be too risky for a boat with a 9 feet draft.

When underway, it is impossible to determine a boat’s draft, so you must measure it beforehand. You should start by calculating how much freight you would commonly carry on the boat.

A boat’s draft is influenced by a multitude of variables, including the amount of weight on board; the heavier the boat is, the lower it rides in the water, resulting in a deeper draft. Estimating the draft using the maximum weight that would, as a rule, be carried on the boat is an effective technique for ensuring that nothing gets wrong. This method is effective in avoiding excessively shallow water.

Calculate the draft of your boat: A complete guide

Items are used to calculate the draft of your boat.

  1. Measuring Tape
  2. Calculator 

 Step 1: Assume the boat is empty and measure the distance from the bottom of the hull to the waterline. For example, the distance is 5 feet.

 Step 2: Secondly, measure the length and width of your boat’s deck with the measuring tape. Then you have to multiply the length and width measurements to calculate the deck’s area. For example, the length of the deck of your boat is 15 feet, and the width of the deck of the boat is 5 feet. Then the area of the deck of the boat is 75 feet.

 Step 3: Thirdly, you must determine the unit weight of the water you travel in. If you are traveling in salt water, you have to divide the weight of each object or a person with the unit weight of that salty water.

Saltwater has a unit weight of 29 kg per cubic foot. If you are traveling in freshwater, the unit weight of fresh water is 28.3 kg per cubic foot. For example, two people traveling on a boat weighing 70kg and 90kg, respectively.

You have to divide the person’s weight with the unit weight of salt water. When you divide 70 by 29, you will get 2.41, and when you divide 90 by 29, you will get 3.10. After calculating, you have to add both calculations, and you will get the total volume of the water displaced by the boat. So, you will get 5.51.

Step 4: After calculating the total volume, you have to divide the total volume of the water displaced by the surface area of the boat’s deck, which we discuss in step 2. So you have to divide 5.51 by 75 feet and get 0.073.

Step 5: In the final step, you have to add the results of steps 1 and 4 to obtain the draft of your boat. The draft of your boat traveling in salt water with two people weighing 70kg and 90 kg is 5.073 feet. You would add 5 to 0.073.

These are the main steps through which you can easily measure the draft of the boat.

Average boat drafts

Knowing these averages will help you avoid damage to your damage as well as any accident in the water:

 Low Draft: A boat 32 feet long or less needs 3 feet or less of water

  • Medium Draft: A boat 45 to 65 feet long needs 4 to 5 feet of water
  • High Draft: A boat 65 feet long or greater needs 5 to 7.5 feet of water

 So the average boat draft for a cruising sailboat is 5’ while for a cabin cruise is 3’.

The final verdict!

If you are a fan of cruising and going into the shores, worry not, as we have got you covered! Now you can go as deep into the sea as you want but with a little precaution. Drafting helps you find how deep your boat can dive into the water.

Safety before anything! Hence we have explained an easy method you can use to measure the draft of the boat and enjoy your trips. Familiarize yourself with this method and research further with the help of tutorial videos and become a pro. A study shows that about 142 million Americans went into the water for boating in 2016. Hence knowing how to measure the draft of the boat is a must to stay safe.