The below Berger Twist Rate Stability Calculator allows you to identify what the optimal twist rate and the marginal twist rate is for any given bullet given your shooting conditions. This tool allows you to figure out which bullets will stabilize out of your rifle given your rifle’s twist rate. This tool also helps you to identify which barrel twist rate you want to buy if you already know which bullet you plan to shoot.

For additional information, we recommend you read our guide on how to use the Berger Twist Rate Calculator.

Important Note: The Miller Twist Rate Formula isn’t accurate with flat based bullets, so we recommend you view our flat based bullet twist rate chart to identify what the minimum twist rate is for all of our flat based bullets.

Bullet Library

Select a bullet from the list or enter in the properties below

Bullet Parameters


[?]Ballistic Coefficient
Ballistic Coefficient (BC) to either the G1 standard or the G7 standard. If both G1 and G7 data are provided, it is best to choose the G7 value for HPBT type bullets.



[?]Bullet Caliber
The diameter of the bullet as provided by the manufacturer.


[?]Bullet Weight
The weight of the bullet as provided by the manufacturer.



[?]Bullet Length
The length of the bullet as provided by the manufacturer. If unknown, mulitiply bullet diameter by 4.2.

Gun and Atmospheric Parameters

Muzzle Vel.

[?]Muzzle Velocity
How fast the bullet leaves the rifle as measured by a chronograph. For very accurate results, remember to account for the velocity lost in the 10-15 feet between the muzzle and the chronograph. As a rule of thumb, a bullet looses 5-15 fps in this short distance.

Barrel Twist

[?]Barrel Twist
How many "inches per turn" is your rate of rifling twist. This number is used along with other inputs to determine the stability and related trajectory metrics. Typical value for this input is between 1:7" and 1:13".



[?]Air Temperature
The atmospheric temperature. Because there is a great sensitivity to atmospheric temperature, it is recommended that this data be provided by using a local weather station or handheld weather meter.


The altitude at which the shooter is at. The ICAO standard is used to find the standard atmospheric pressure at the given altitude and temperature.

Stability Analysis