Use one coordinate reference
Locate every component’s centre from the same origin. Negative coordinates are allowed on the opposite side of an axis.
LIFTING & RIGGING / TOOL 07
Combined Centre of Gravity Calculator
Use this when a load consists of up to three components whose individual masses and centres of gravity are known. It locates their combined centre in a horizontal coordinate system.
Before you start: required inputs
- Choose an origin on the plan and mark consistent positive x and y directions.
- Obtain each component’s mass and its own centre-of-gravity location from a drawing, balance measurement or verified equipment data.
Calculation diagram
A PRACTICAL WALKTHROUGH
How to use this calculator
Describe the mass groups
Enter each component’s mass and x/y coordinates. Set an unused mass group to zero.
Locate the combined point
Plot the resulting x and y on the same drawing. Use the combined mass to verify that no component has been omitted.
Two components on one horizontal line
THE INPUTS
Group 1: 1,000 kg at (0, 0) m; group 2: 2,000 kg at (2, 0) m; group 3: 0 kg.
THE RESULT
Combined mass is 3,000 kg. The combined centre of gravity is at x = 1.33333 m and y = 0 m, nearer the heavier component.
What does the result mean?
01
The x and y results are coordinates from your chosen origin, not distances from the outer edge of the complete load unless you chose that edge as zero.
02
A heavier component pulls the combined centre of gravity toward its own centre.
03
The result is a two-dimensional mass balance; it does not by itself establish stable lifting points or load orientation.
Watch for this
Using each component’s outside corner instead of its own centre of gravity, or measuring different groups from different origins.
Formula & model conditions +
xCG = Σ(m × x) / Σm
yCG = Σ(m × y) / Σm
- Each mass group is represented at its known centre of gravity.
- All coordinates use the same origin, axes and length unit. Negative coordinates are allowed.
- This two-dimensional mass balance does not assess rotational stability or determine lifting-point suitability.
Common questions
Can I include a fourth component?
Combine two or more components into a subgroup using their calculated total mass and centre, then use that subgroup as one of the three groups.
Does this find the vertical centre of gravity?
No. This form calculates x and y in your selected horizontal plane; it does not model the vertical coordinate or overturning stability.