Which Tool Do You Need?
FixItHub has 10 separate calculators instead of one generic "project calculator" because materials work differently — concrete is bought by volume, drywall by sheet count, mulch and gravel by different depths and units entirely. This guide maps your project to the right tool, grouped by the four categories on the site, plus a worked example that chains several tools together for a real room.
Building materials
- Pouring a slab, footing, or post hole? The Concrete Calculator gives you cubic yards and 60 lb / 80 lb bag counts from length, width, and thickness.
- Framing and hanging drywall? The Drywall Calculator works out 4×8 ft sheet count and screws from your room's dimensions, with an optional ceiling toggle.
Finishing a room
- Painting walls? The Paint Calculator figures gallons needed from room size, doors, windows, and number of coats.
- Installing hardwood, laminate, or vinyl plank? The Flooring Calculator converts square footage into boxes, with an adjustable waste factor for cuts.
- Tiling a floor or wall? The Tile Calculator gives you an exact tile count from your tile's dimensions, plus a rough grout estimate.
Outdoor projects
- Mulching garden beds? The Mulch Calculator converts bed size and depth into cubic yards or 2-cubic-foot bags.
- A driveway, path, or gravel base layer? The Gravel Calculator gives cubic yards and an estimated weight in tons.
- Building a fence? The Fence Calculator works out post count (correctly — it's always gaps + 1) and total rail length.
Home systems
- Sizing an air conditioner or heater? The BTU Calculator estimates capacity from room size, insulation, sun exposure, and occupants.
- Wondering what an appliance actually costs to run? The Electricity Cost Calculator turns wattage, hours used, and your rate into daily, monthly, and yearly costs.
Worked scenario: finishing a 300 sq ft basement
Finishing a basement is exactly the kind of project that needs several of these tools in sequence, not just one. Say the room is 20 ft × 15 ft with 8 ft walls, 1 door, and 2 small egress windows.
- Start with the Drywall Calculator for the walls: perimeter wall area is 2 × (20 + 15) × 8 = 560 sq ft, minus 21 for the door and 30 for the two windows, leaving 509 sq ft. Divided by 32 sq ft per sheet and rounded up, that's 16 sheets (about 764 screws).
- Next, the Flooring Calculator for the floor: the room's 20 × 15 = 300 sq ft footprint, plus the default 10% waste factor, comes to 330 sq ft. At 20 sq ft of coverage per box, that rounds up to 17 boxes.
- Then the Paint Calculator for the walls: using the same 509 sq ft paintable area (the tool subtracts doors and windows the same way) at 2 coats, that's 1,018 sq ft of total coverage. Divided by 350 sq ft per gallon and rounded up, you need 3 gallons.
- Finally, the BTU Calculator to check whether a space heater is enough for the room: 300 sq ft at the 20 BTU/sq ft baseline is 6,000 BTU. Basements are typically shaded (no direct sun) and this one sees regular use by 4 people on movie nights, so the shaded multiplier (×0.9) and the occupant adjustment (600 BTU for each person past two) bring it to about 6,600 BTU — look for a unit rated around 7,000 BTU. Treat that as a browsing range, not a purchase spec — see the FAQ below.
All FixItHub tools
- Concrete Calculator Work out how many cubic yards or bags of concrete you need for a slab, footing, or post hole.
- Paint Calculator Find out how many gallons of paint you need for a room, including coats and trim.
- Flooring Calculator Calculate the square footage and boxes of flooring you need, with a waste-factor buffer.
- Tile Calculator Find how many tiles, how much grout, and how much adhesive a floor or wall needs.
- Drywall Calculator Work out how many drywall sheets, screws, and joint compound a room needs.
- Mulch Calculator Find the cubic yards or bags of mulch you need for your garden beds.
- Gravel Calculator Calculate the tons or cubic yards of gravel needed for a driveway, path, or base layer.
- Fence Calculator Find the posts, rails, and panels you need for a fence of any length.
- BTU Calculator Estimate the heating or cooling BTU capacity a room needs based on its size.
- Electricity Cost Calculator Find out what it really costs to run an appliance, from its wattage and your electricity rate.
Frequently asked questions
Does the flooring calculator account for waste and cuts?
Yes — it has its own editable waste-factor field, defaulting to 10%. That default sits in the middle of the 7-15% range contractors commonly budget for cuts along walls, mis-cuts, and pattern matching. A plain straight (running-bond) layout can often get by near the low end; herringbone, diagonal, or angle-heavy rooms usually need the higher end, so bump the percentage up before you order.
What's the difference between the mulch and gravel calculators if they're both just volume from an area?
The geometry step is the same, but the materials and conventions differ enough to need separate tools. Mulch is typically spread 2-3 in deep and sold in 2-cubic-foot bags, so the Mulch Calculator reports cubic yards and bag counts. Gravel goes down thicker — 4 in for a base layer, up to 6-8 in under a driveway — and is dense enough that suppliers price and deliver it by weight, so the Gravel Calculator adds a tons conversion (using a common 1.4 tons-per-cubic-yard average) that mulch never needs. Same math skeleton, different real-world units.
Why is there a separate concrete calculator and drywall calculator instead of one generic volume calculator?
Because the two materials are bought under completely different unit logic, not just relabeled versions of each other. Concrete is a pourable volume — it's ordered in cubic yards or counted in 60/80 lb bags with a published dry-mix yield, and the calculator does not build in a waste buffer since pros typically pad each pour by hand for their specific forms. Drywall is a sheet-goods material — the tool works out wall area, subtracts standard door and window openings, then divides by a fixed 32 sq ft (4×8 ft) sheet size and rounds up to a whole sheet count. One is genuine volumetric math; the other is area-to-sheet-count math. Forcing both into one "volume calculator" would get the drywall math wrong.
Why do the flooring and tile calculators include an adjustable waste factor, but the concrete calculator doesn't?
It comes down to how predictable the waste is. Flooring and tile are cut to fit a fixed room shape every time, so a percentage-based buffer (7-15% for flooring, similarly for tile) is a reliable, repeatable estimate — which is why both tools bake in an editable waste-factor field. Concrete waste depends much more on job-specific variables — how square your forms are, how even the subgrade is, how much spills during the pour — so instead of guessing a universal percentage, the Concrete Calculator gives you the raw volume and lets you add your own 5-10% pad, as covered on that tool's page.
Does the BTU calculator work for sizing a heater, or is it just for air conditioning?
Both, with the same caveat either way. The calculator's 20 BTU-per-square-foot baseline is commonly cited as a starting point for cooling and heating loads alike, and it adjusts for insulation, sun exposure, occupants, and ceiling height regardless of which direction you're using it. Heating loads do tend to be more sensitive to climate zone and window count than cooling loads, so treat the result as a browsing range rather than a purchase spec — a full Manual J load calculation from a professional is the real standard before you buy a furnace, heat pump, or AC unit.