Trapezium Calculator

This Trapezium calculator is multi-purpose	This is also a reverse Trapezium calculator
It will calculate any size of dome and display the lengths for each strut, total amount of material required, the weight of your geodesic dome and even the amount of material to cover your geodesic dome.	Enter any value in any yellow box and it will calculate all other corresponding values. For example you can specify a 2-foot length for strut “B” and all other struts and related values will be calculated.

NOTE: If you enter a measure in feet, your results are in feet or, in the case of floor area, square feet. Same goes for meters. When entering in feet, decimals are fractions of a foot or square foot (for example: 2.75 = 2’9″).


Spherical radius
Spherical diameter
Floor area
Perimeter


feet of pipe / lumber

NOTE: if you are bolting conduit, regardless of dome size, add an extra 32 feet or 10 meters to total above (based on 3″ or 8cm for each strut)
		ANGLE
16 X “A”		10.38°
16 X “B”		7.93°
16 X “C”		4.28°
80 X “D”		11.25°
Total number of struts: 128

For conduit, you can round bend angles to the nearest degree. For timber domes, angles should be to the nearest tenth of a degree.

See assembly diagrams at bottom of this page

Struts are vertex to vertex

That means end to end. But to connect them together with bolts, you need to make them longer to drill holes in them.

Connecting struts Many types of connectors are available for steel and timber Trapezium. For more information, click here.
If you use hubs	1 X 16-way connectors	48 X 4-way connectors	16 X 3-way connectors
OR

If you bolt struts together	65 bolts	65 nuts	130 washers
For more information on cutting, bending and flattening struts, click here

Your calculated floor surface area is

SQUARE FEET/METERS

NOTE: RESULTS IN THIS SECTION ARE BASED ON FEET.

Estimated standing capacity
Estimated dining capacity
Estimated conference capacity

How much will your Trapezium weigh?
Your calculated Trapezium diameter is
NOTE: RESULTS IN THIS SECTION ARE BASED ON FEET.
	1/2″	3/4″	1″	1 1/4″	1 1/2″	2″
EMT
Wall thickness	0.042″	0.049″	0.057″	0.065″	0.065″	0.065″
Lbs.
kgs.
STEEL SCHEDULE 40
Wall thickness	0.109″	0.113″	0.133″	0.140″	0.140″	0.154″
Lbs.
kgs.
ALUMINUM SCHEDULE 40
Wall thickness	0.109″	0.113″	0.133″	0.140″	0.140″	0.154″
Lbs.
kgs.

The tables show sample costs. Material prices vary with suppliers and area.

Your calculated Trapezium requires

feet (or meters) of pipe / lumber

NOTE: THIS SECTION ONLY ESTIMATES COST IN FEET.

Galvanized pipe – Steel Schedule 40
Your estimated pipe dollar cost is:
1/2″ @ $13 /10′ length
3/4 @ $17/10′ length
1″ @ $25 /10′ length
1 1/4″ @ $34 /10′ length
1 1/2″ @ $42 /10′ length
2″ @ $55 /10′ length

Structure pipe – Aluminum Schedule 40
Your estimated pipe dollar cost is:
1/2″ @ $ /10′ length
3/4 @ $ /10′ length
1″ @ $ /10′ length
1 1/4″ @ $ /10′ length
1 1/2″ @ $ /10′ length
2″ @ $ /10′ length

Structure pipe – EMT
Your estimated pipe dollar cost is:
1/2″ @ $5.50 /10′ length
3/4 @ $ 8.80 /10′ length
1″ @ $18 /10′ length
1 1/4″ @ $19 /10′ length
1 1/2″ @ $22 /10′ length
2″ @ $3 2/10′ length

Cover: approx. s.f.

	$ COST
Canvas 20 oz. ($1/s.f.)
Canvas 42 oz ($1.50/s.f.)
Poly 3 mil ($0.05/s.f.)
Poly 6 mil ($0.06/s.f.)
Marine Shrink Wrap 7 mil. ($0.08/s.f.)
Industrial fire-retardant Shrink Wrap 12 mil ($0.23/s.f.)
Aluminet 70% shade cloth ($0.35/s.f.)
Tyvek (housewrap) ($0.41/s.f.)
Plywood 1/2″ ($25/ 4′ X 8′)

Wood struts
Your estimated wood dollar cost is:
2″X4″ @ $0.35 foot (avg.)
2″X6″ @ $0.50 foot (avg.)
2″X8″ @ $0.70 foot (avg.)
Flooring:
Plywood 1/2″ ($25/ 4′ X 8′)
OSB 1/2″ ($9/ 4′ X 8′)