Mr. Rogers' IB Design Technology

Elements of a Detailed Materials Cost Estimate

A materials list should give all the details needed to accurately estimate costs and to accurately determined budgets. It should be done with a spread sheet and contain the following columns:

Headings fro the Cost Estimate

Number: The number of units to be ordered

Quantity: The size of a unit. For example dozen, box, carton, 10-pack, each, etc.

Price: The cost of one unit of the item

Item: A detailed description of the item to be ordered including part or model numbers.

Vendor: where the item is to be purchased. It's not necessary to list all the details on each vendor for each item. A code can be listed with the details can be footnoted.

Total: Number x Price the amount to be paid. Shipping and taxes are usually listed as a separate item. If shipping is unknown estimate it at 8 to 10%.

See example below:

Items in the Cost Estimate

Major Purchases - These are typically any item which makes up 5% or more of the project's material cost.

Tax - should be added where appropriate.

Shipping - should be added when known except for local pick up and delivery items. If shipping is unknown, use 8%

Misc. - small items like fasteners, paint wire, etc. can be lumped together but should not be ignored

Contingency - for items like unforeseen price increases. Contingency should not be used to cover for a sloppy or hasty cost analysis.


Cost Estimate Example

Num  Quantity Item Vendor Price ($) Total ($)
2 each 1/4 x 2 in bolts Acme Hardware 0.13 0.26
4 each 1/4 in nuts Bob's Hardware 0.05 0.20
    Tax     0.01
    Shipping     1.00
    Total     1.47

Materials sources:

McMaster Carr - has a huge selection of industrial components.

Javalin Stamp Computer - a very powerful tiny computer which can be programmed in a subset of Java. It can be used for sensors,  motor speed control, and many other applications

ER-1 Robot - the basis for SAM jr.

Robot MarketPlace - a good source of parts and ideas for robotics applications