G to RPM Calculator

Enter calculation values

A g-force value cannot be converted to RPM without a rotation radius. Measure from the axis to the point where the sample or mass experiences acceleration.

G-force → RPM

RPM → G-force

G-force (RCF) Enter multiples of standard gravity, such as 12000 ×g.

Rotation radius

Use the radius to the actual sample or rotating mass.

Radius measurement type Maximum radius usually estimates maximum RCF.

Rotor or system type

Rotor or equipment name

Displayed precision

RPM rounding method

Advanced gravity and equipment limits

Gravity constant Standard gravity is 9.80665 m/s². Use a custom gravity value

Maximum equipment RPM

Maximum equipment RCF

Maximum tangential speed Enter the limit in meters per second.

Example presets

These values demonstrate the calculator. They are not equipment recommendations.

Saved rotor profiles

Profiles are stored only in this browser. They help reuse common radius, rotor, gravity, and equipment-limit settings.

Calculation history

Recent calculations are stored locally on this device. Use any entry to refill the form.

How the radius is measured

Measure the rotation radius from the center of the axis to the point where the sample, bucket, tube, or mass experiences centrifugal acceleration.

A swinging-bucket rotor may have different minimum and maximum radii. Use the operational radius that matches the sample’s position during rotation.

Using diameter instead of radius doubles the distance. That mistake changes the calculated result substantially.

Example data table

Application example	G-force	Radius	Approximate RPM
Small laboratory centrifuge	1,000 ×g	8 cm	3,343 RPM
Microcentrifuge	12,000 ×g	7.5 cm	11,962 RPM
High-speed centrifuge	25,000 ×g	10 cm	14,952 RPM
Industrial rotating equipment	50 ×g	30 cm	386 RPM

Formula used

For a radius measured in centimeters, the common centrifuge relationship is:

RCF = 1.118 × 10⁻⁵ × r_cm × RPM²

Solving for rotational speed gives:

RPM = √(RCF ÷ (1.118 × 10⁻⁵ × r_cm))

The calculator uses the equivalent SI relationship for all radius units:

RPM = (60 ÷ 2π) × √((RCF × g₀) ÷ r_m)

Where RCF is relative centrifugal force, g₀ is the selected gravity constant, and r_m is radius in meters.

Derived formulas

ω = 2π × RPM ÷ 60
v = ωr
T = 60 ÷ RPM
a = ω²r

How to use this calculator

Select whether you are converting g-force to RPM or RPM to g-force.
Enter the source value using a positive number.
Measure the radius from the rotation axis to the sample position.
Select the correct radius unit and measurement type.
Optionally enter equipment limits, rotor details, or custom gravity.
Choose displayed precision and the preferred RPM rounding method.
Select Calculate to view the main and derived results.
Review warnings before applying any speed to real equipment.
Download CSV or PDF reports when documentation is required.

Understanding g-force, RPM, and rotor radius

What g-force means

Relative centrifugal force compares rotational acceleration with standard gravity. A result of 1,000 ×g means the sample experiences one thousand times standard gravitational acceleration. Laboratories often use RCF because it describes the actual force effect more directly than RPM.

What RPM means

RPM measures revolutions completed during one minute. It describes rotational speed, but it does not fully describe centrifugal acceleration. Two rotors running at equal RPM can produce different g-force when their radii differ.

Why radius changes the result

Centrifugal acceleration increases directly with radius and with the square of rotational speed. Doubling the radius doubles RCF at unchanged RPM. Doubling RPM increases RCF by roughly four times. Small speed changes can therefore cause large force changes.

Minimum, maximum, and average radius

A rotor may expose different sample regions to different radii. Minimum radius refers to the point nearest the axis. Maximum radius refers to the farthest sample point. Average radius estimates the sample center. Manufacturer documentation may specify which radius supports its published RCF rating.

Fixed-angle and swinging-bucket rotors

Fixed-angle tubes remain tilted while rotating. Swinging buckets move outward and become more horizontal at speed. Their operating radius can differ from the resting radius. Use the radius matching the actual operating geometry.

Angular and tangential speed

Angular velocity describes the rate of rotation in radians per second. Tangential velocity describes linear speed at a selected radius. Tangential speed rises with radius even when RPM remains unchanged.

Common mistakes

Frequent errors include entering diameter as radius, selecting the wrong length unit, confusing RPM with RCF, or applying a rounded result above the rotor limit. Check every unit before operating equipment.

Safety considerations

Calculated values do not replace manufacturer limits. Rotor condition, balance, temperature, material fatigue, adapters, and sample mass can affect safe operation. Never exceed the lowest applicable limit. Inspect equipment and follow approved procedures.

Using a custom gravity value

Most calculations should use 9.80665 m/s². A custom value may support specialized demonstrations or non-Earth environments. Changing gravity alters the physical acceleration represented by one g in the selected model.

Interpreting the comparison tables

The speed table demonstrates the squared relationship between RPM and RCF. The radius table holds g-force constant and varies radius. These comparisons help explain why larger rotors often need less RPM for the same RCF.

Frequently asked questions

Can g-force be converted directly to RPM?

No. Rotation radius is required because the same g-force can occur at different RPM values when the radius changes.

Why is the rotor radius required?

Centrifugal acceleration depends on both angular speed and distance from the axis. Radius supplies that necessary distance.

What is the difference between RCF and RPM?

RPM measures rotational speed. RCF measures acceleration relative to standard gravity. RCF also depends on rotor radius.

Should I use minimum or maximum rotor radius?

Use the radius matching your sample position and equipment documentation. Maximum radius usually represents the highest experienced RCF.

Is one g always 9.80665 m/s²?

Standard gravity is defined as 9.80665 m/s². Local gravitational acceleration can vary slightly, but most equipment calculations use the standard value.

Why does required RPM fall when radius increases?

A larger radius produces more centrifugal acceleration at the same speed. Therefore, less RPM is needed for an unchanged target RCF.

Can this calculator be used for centrifuges?

Yes, for mathematical conversion. Confirm the result against rotor documentation and never exceed specified RPM, RCF, loading, or maintenance limits.

How accurate is the calculated RPM?

The formula is precise for the entered values. Real accuracy depends on radius measurement, instrument calibration, rounding, rotor geometry, and equipment behavior.

Important safety notice

This calculator provides mathematical estimates. It does not certify safe equipment operation. Always follow manufacturer instructions, inspect rotors, balance loads, use rated accessories, and respect the lowest published limit.