PreConstruct AIFor instructors
Free estimating calculators and guides for your course
9 calculators and 12 guides that show their arithmetic, in metric and imperial, with Canadian bar sizes and Ontario code references. Free to use, link and put on screen in class, with no account.
What students can do with them
- Check a hand takeoff against a calculator that prints every step, so the method is what gets marked, not only the answer.
- Work between imperial and metric: cubic yards and cubic metres, CSA 10M to 55M bars by the kilogram, psi and MPa.
- Read the schedules a takeoff starts from: partition types, footing schedules, door and room schedules.
- Lay out a stair against Ontario's rise and run limits, with the edition caveat a code reference needs.
The tools count and measure from the sizes typed into them. They never choose a stud gauge, a bar or a footing: sizes come from the drawings and the engineer, which is the habit a course is trying to build.
Free calculators
- Concrete calculator
Slabs, footings, walls, pads, columns and stair flights — cubic yards, cubic metres and the half-yard order.
- Drywall calculator
Sheets by size, screws, tape and joint compound for walls and ceilings, less openings, at your own rates.
- Stair stringer calculator
Riser height, total run and stringer length from the total rise, risers and tread — checked against Ontario's riser limits.
- Rebar weight calculator
CSA 10M to 55M and ASTM #3 to #11: bars by length or a slab mat each way, in kilograms, pounds and tonnes.
- Metal stud calculator
Steel studs at your spacing, extras at openings and corners, and top and bottom track in 10 ft pieces.
- Insulation calculator
Bags of R14, R22 or R24 batts for walls and ceilings, less openings, at the coverage on the bag.
- Paint calculator
Finish and primer for walls and ceilings in 3.78 L cans or 18.9 L pails, from the coats and the data sheet.
- Concrete block calculator
8 × 16 or 20 cm metric block, mortar bags and core grout in cubic yards and cubic metres.
- ICF calculator
Insulated concrete forms, straight and corner, and the concrete for the core, rounded to the half yard.
Guides
- How to read a footing schedule
Marks, sizes and reinforcing — strip footings and pads, metric and imperial — and how to take off each row.
- Concrete takeoff: footings, walls, slabs and rebar
Volumes in cubic metres and yards, forms by contact area, Canadian rebar weights, and the Ontario code minimums to check.
- How to estimate framing for a house
Walls, openings, floors, roofs, stairs, hardware and labour — the counts framers use and what gets missed.
- Drywall takeoff checklist: what goes missing
Twelve things that fall off interior takeoffs — backing, headers, control joints, clouds and eight more — and how to catch them.
- How to read a partition schedule
Studs, board layers, insulation, height and ratings — and how each partition type becomes material.
- Drywall per square metre
Square metres per sheet, screws, tape and compound per m², and a worked metric example.
- Canadian rebar sizes: 10M to 55M
Diameter, area and kg per metre for every CSA bar, what a 6, 12 or 18 m bar weighs, the nearest US bar, and a footing worked through.
- Drywall screws per square metre
The Ontario spacing rules turned into screws per sheet and per m², fire-rated work, Type W or S, screw length and a worked order.
- Steel stud gauge chart and sizes
Gauge to mils and millimetres for 25, 20 and 18 gauge, the two different 20 gauges, EQ studs, sizes in inches and mm, and studs and track per metre.
- Ontario stair rise and run
Rise, run, headroom, width, landings, handrails and guards under the Ontario code, what changed in 2022, and a stair laid out in millimetres.
- How to read an addendum before you bid
Find every change on the revised drawings and specs, and carry it into the takeoff before close.
- Choosing takeoff software as a subcontractor
What to compare before you buy: metric and imperial, trade assemblies, pricing by seat or by job, and what AI really does.
Using them in a course
Link to any page directly, from a course page, a syllabus or an assignment. Nothing needs an account, and the guides list their sources at the foot of the page.
If a worked example or a calculator would help your students and is not here, tell us what it is.