How to Calculate Drone Motor Thrust Step by step guide

 

In our previous articles, we repeatedly mentioned that the motor is the core power system of the drone, which determines whether the drone can fly, how stable it is in the air, whether it can carry weight, and how long it can fly. You already know what a brushless DC motor (BLDC) is, how drone motors work, and how to choose different types of drone motors...

 

Now, it's time to take a closer look at another key parameter: thrust.

 

Thrust determines whether a drone can take off and hover, and also determines whether you can mount cameras, mapping modules, load cargo and other mission equipment.

 

Insufficient thrust → cannot fly; too much thrust → wastes energy and shortens endurance.

Only with appropriate thrust can the motor, propeller, electric speed controller and battery form a stable and efficient system.

 

In the following section, we will teach you the core ideas of thrust evaluation step by step, from the definition of thrust, motor power calculation, thrust-to-weight ratio recommendations, to ESC matching methods.

 

In physics, thrust is the force that pushes an object forward or upward, and its unit is usually Newton (N) or gram (g)/kilogram (kg). In the drone industry, we more often use "grams" or "kilograms" to measure the thrust of the motor, which directly reflects how much weight it can "lift".

 

1. Basic definition of thrust

Thrust = Motor + propeller upward force at a certain input power

 

For example:

If a motor produces 1000g of thrust, it means that it can "lift" a weight of less than 1kg under static conditions.

 

The thrust of each motor of a quadcopter is 1000g, and the total thrust is 4000g (4kg), which can theoretically support a maximum take-off weight of 2kg (thrust-to-weight ratio of 2:1).

This value is directly related to the aircraft's "take-off capability" and "load capacity".

 

2. Static thrust vs dynamic thrust

In practical applications, we often distinguish between static thrust and dynamic thrust:

type	Definition	Test method
Static thrust	The thrust generated by the motor + propeller in still air	Placed on the thrust test platform
Dynamic thrust	The thrust that the motor + propeller can provide in flight/motion	Wind tunnel or aerial measurement (more complex)

The motor thrust value we often talk about usually refers to the "static thrust", which is also the standard data tested and published by motor manufacturers.

 

3. Thrust-to-weight ratio: a key indicator for selecting a motor

Thrust-to-weight ratio = total thrust ÷ takeoff weight, is an important indicator for evaluating flight performance:

Flight use	Recommended thrust-to-weight ratio	illustrate
Aerial photography/mapping drone	2:01	Ensure hovering and load stability
Industrial reconnaissance/highland operations	2.5:1 ~ 3:1	Improve redundancy to cope with changes in air pressure/environment
Racing FPV Drone	4:1 ~ 6:1	Rapid acceleration and intense maneuvers require a high thrust-to-weight ratio

For example, for an aerial photography drone with a takeoff weight of 1500g, the recommended total thrust is about 3000g, which means you need to choose a solution where each motor can provide at least 750g of static thrust.

 

To understand the mechanism of motor thrust generation, you must understand a basic physical relationship:

Motor power (W) = voltage (V) × current (A)

 

The generation of thrust is essentially that after the motor consumes a certain amount of electrical power, it accelerates the air downward through the propeller, thereby generating an upward reaction force. The greater the thrust, the higher the power consumption, the greater the current, and the faster the temperature rise.

 

1. The influence of voltage, current and power on thrust

parameter	Impact Statement
Voltage (V)	The higher the voltage, the higher the power output when the current is the same → more suitable for large thrust platforms
Current (A)	Indicates the current load intensity of the motor. The greater the load, the more power it consumes and the higher the temperature rise. It needs to be matched with sufficient ESC.
Power (W)	The greater the power, the greater the thrust in theory, but be careful whether it exceeds the limits of the motor and ESC.

 

Thrust enhancement cannot be achieved by simply increasing a single parameter. For example, simply increasing voltage or current may cause overheating, ESC burning, battery voltage drop, or even loss of flight control.

 

2. The relationship between KV value and thrust: Don't be confused by "high speed"

KV value (RPM/V) indicates the speed that the motor can reach when the motor is under no-load condition and the input voltage is 1V. For example, for a 1000KV motor, the theoretical speed is 10,000 RPM at 10V voltage.

 

High KV value: high speed, but low torque, suitable for small propellers, light loads, and racing scenarios;

 

Low KV value: low speed but high torque, suitable for large propellers, large thrust and load-bearing platforms.

Misconception: A higher KV does not necessarily mean greater thrust. The real thrust depends on the power and efficiency that the motor can continuously output under a certain load (propeller).

 

3. Example analysis: Thrust differences of different KVs on the same platform

Take two VSD motors as an example:

model	KV value	Voltage range	Maximum Power	Maximum thrust	application
2306	2400KV	6S	901W	1683g	FPV Racing Machine
3115	900KV	6S~8S	1617W	4185g	Multi-rotor aerial photography

 

With the same 6S voltage, although the 2306 has a high speed, its thrust is obviously lower than that of the 3115. This is the best explanation that the KV value is not proportional to the thrust.

 

Calculating motor thrust is not as "metaphysical" as many people think. Even if you don't have sophisticated testing equipment, as long as you master basic logic, reference data and reasonable estimates, you can make a preliminary judgment on whether a motor is suitable for your drone project.

 

We teach you at three levels:

1. Thrust-to-weight ratio estimation method (applicable to most application scenarios)

This is the most common and practical basis for selection:

Recommended total thrust = takeoff weight × recommended thrust-to-weight ratio

Flight Type	Recommended thrust-to-weight ratio
Aerial photography/mapping	2:01
Cargo/Industrial Investigation	2.5–3:1
Racing through	4–6:1

 

example:

You are going to assemble a quadcopter drone for aerial photography. Its takeoff weight when fully loaded is 2.2 kg.

The recommended thrust-to-weight ratio is 2:1, so you need a total thrust ≥ 4.4kg (4400g).

Then the minimum thrust of each motor should be: 1100g.

 

2. Table comparison method (applicable when there is manufacturer test data)

If you choose a motor with detailed test data, such as the VSD series, you can directly refer to its maximum static thrust parameters and compare them with your needs.

Motor Model	Recommended voltage	Maximum thrust	Recommended maximum load (thrust-to-weight ratio 2:1)
3115	6S–8S	4185g	≤ 2.1kg
2808	6S	2910g	≤ 1.45kg
2306	6S	1683g	≤ 0.8kg

 

In this way, you can quickly filter out the range of motors that meet the load requirements of the entire machine.

 

3. Manual calculation method (for detailed estimation or DIY users)

If you are very sensitive to the parameters, or do not have ready thrust data, you can also estimate it based on the following relationship:

(1) Power method estimation:

Theoretical thrust ≈ C × √(power × propeller diameter)

Where C is an empirical coefficient, usually ranging from about 6 to 9. The larger the propeller, the higher the efficiency.

 

Example: You estimate the maximum motor power to be 1600W with a 13-inch propeller.

The estimated thrust is ≈ 7 × √(1600 × 13) ≈ 7 × √20800 ≈ 7 × 144 ≈ 1008g

 

This method is suitable for approximate estimation, and the actual thrust still needs to be based on actual measurements.

 

Once you have determined the required thrust and motor model, the next step is to consider the matching of the supporting system, especially the ESC and battery. If the ESC current is insufficient and the battery output is unstable, the system will not work stably even if the thrust is sufficient.

 

Here are three core matching principles:

1. ESC current must be greater than the maximum motor current

ESC current rating should exceed the motor's maximum continuous current by a factor of 1.2 to 1.5

 

Practical advice: Choose an ESC that is 20-50% higher than the motor's maximum current

 

example:

VSD 3115 motor, maximum current is about 50A

→ Recommended ESC current ≥ 60A

 

VSD 2306 motor, maximum current is about 35A

→ Recommended ESC current ≥ 45A

 

Note: Although choosing an ESC that is too large is safe, it may also increase weight and power consumption, resulting in efficiency waste.

 

2. The battery voltage should match the motor KV value and the use environment

The KV value determines how many S batteries you should use (1S = 3.7V). Choosing the wrong battery voltage will result in insufficient thrust or overload and burnout.

KV Range	Recommended battery S number	Application suggestions
800–1000KV	6S ~ 8S	Medium and large-scale aerial photography/surveying
1300–1500KV	4S ~ 6S	Multi-rotor platform
1800KV and above	4S ~ 6S	FPV racing, light aircraft

 

example:

VSD 4720 motor, 420KV → 6S ~ 8S recommended

VSD 2808 motor, 1500KV → 6S recommended

VSD 2306 motor, 2400KV → 4S or 6S recommended (depending on the task requirements)

 

3. Propeller size affects thrust efficiency and system load

The larger the propeller size, the greater the torque and thrust, but the greater the burden on the ESC and motor. It is recommended to choose a reasonable propeller type combination based on the test data provided by the manufacturer.

 

Combined with VSD motor cases, quickly complete the thrust and supporting system selection

In the previous sections, we explained the definition of thrust, calculation method, voltage-current relationship, and how to select ESC and battery. Now, we will use the real data of VSD drone motors to show you a practical selection logic.

 

The following are some typical models of matching selection suggestions, suitable for different flight scenarios from light cross-country drones to large multi-rotors:

Motor Model	KV value	Voltage recommendations	Maximum thrust	Recommended propeller blades	Recommended ESC current	Applicable scenarios
2306 Drone Motor	1800–2400KV	4S~6S	1683g	5×4.3×3 three-blade propeller	≥ 40A	FPV Racing/ Drone
2808 Drone Motor	1300–1950KV	6S	2910g	7-9 inch propeller	≥ 45A	Medium Racing/ Small Load Multirotor
2207 Drone Motor	1960KV	6S	1702g	5 inch propeller	≥ 40A	Racing drone
3115 Drone Motor	900–1520KV	6S~8S	4185g	13×6.5 propeller	≥ 60A	Aerial photography/reconnaissance drones
2812 Drone Motor	900KV	6S	2710g	10-12 inch propeller	≥ 50A	Medium load aerial photography/industrial flight platform
2807 Drone Motor	1350–1750KV	4S~6S	2728g	6-8 inch propeller	≥ 50A	High maneuverability multirotor / flexible platform
4720 Drone Motor	420KV	6S~8S	7232g	15×7×3 or 13×9×3	≥ 80~100A	Medium and large aerial survey/commercial platform
5315 Drone Motor	380KV	6S~12S	9034g	18×5.5 Propeller	≥ 100A	Industrial grade payload drone/delivery platform

 

Note: The ESC current value in the table is recommended to be ≥ the maximum motor current × 1.2~1.5. The propeller size is recommended based on the test efficiency. The actual selection should be fine-tuned based on the load, flight time and body structure.

 

Selection tips reminder:

 

If you are concerned about battery life, you should give priority to the low KV + large propeller combination;

 

If you are looking for explosive power or racing response, choosing high KV + small propeller will be more agile;

 

It is recommended to use high C-rate batteries to avoid current bottlenecks affecting thrust performance.

 

The ESC needs to have enough current to prevent it from burning out due to long-term heavy load.

 

At VSD, we have provided complete test data and supporting recommendations for each model to help you quickly complete power system selection and reduce trial and error costs.

 

For detailed datasheets, thrust performance curves, or custom power system recommendations, feel free to contact our team. We offer full support for OEM/ODM clients-from design consultation to mass production. We provide one-stop support from solution matching to mass production for OEM/ODM customers.