ToolboxCalc
Material and code calculators for building, electrical and garden work — each one shows the density, rate or code table it used, so you can check the answer before you order or install anything.
Building
- Concrete Slab CalculatorEnter the slab dimensions to get cubic yards, bag count by bag size, and an estimated material cost.
- Concrete Driveway CalculatorDriveways carry wheel loads, so they are thicker than a patio. Enter the dimensions for cubic yards, bag count a
- Concrete Footing CalculatorEnter the total run of footing, its width and thickness. Use the runs field if you have several identical footin
- Post Hole Concrete CalculatorEnter the hole size and post dimension. This subtracts the volume the post occupies, which most calculators skip
- Concrete Steps CalculatorEnter the step width, count, rise and tread. This uses the real staircase volume, not one block per step.
- Concrete Wall CalculatorEnter the wall dimensions and the total area of any windows or doors to deduct.
- Concrete Column & Pier CalculatorFor round forms, piers and tube footings. Enter the diameter, the height of the pour and how many you are placin
- Gravel CalculatorEnter the area and depth. You get loose cubic yards, tonnage at a real density, and a cost if you know your yard
- Gravel Driveway CalculatorA gravel driveway is built in lifts, not as one dump of stone. Enter the depth of each layer to get the total to
- Paver Base CalculatorEnter the paver area and your base depth. This sizes the crushed stone only — bedding sand is a different materi
- Sand CalculatorEnter the area and depth for cubic yards, tonnage and a 50 lb bag count.
- Mulch CalculatorEnter the bed dimensions and depth for cubic yards and a bag count.
- Topsoil CalculatorEnter the area and depth. The settlement allowance accounts for screened soil consolidating after it is spread a
- Asphalt Driveway CalculatorAsphalt is ordered by the ton, hot. Enter the area and the compacted surface thickness.
- Cubic Yard CalculatorThe plain version: dimensions in, cubic yards out. Use this when you know your own material density or your supp
Electrical
- Voltage Drop CalculatorPick a wire size and the calculator looks up its resistance for you, then says whether the drop is inside the 3%
- Wire Size CalculatorEnter the load and the distance. This checks ampacity and voltage drop separately and tells you which one is act
- Watts, Amps and Volts CalculatorConvert watts to amps or back, single or three phase, and get the breaker size including the continuous-load mul
- Ohm's Law CalculatorEnter the two values you know, choose what to solve for, and the formula used is shown with the answer.
- Conduit Fill CalculatorPick the conduit and the conductors. This looks up both areas and applies the right fill limit for your conducto
- Conduit Size CalculatorTell it what you are pulling and it finds the smallest conduit of that type which passes the fill limit.
- Box Fill CalculatorCounts conductors, devices, grounds and clamps the way NEC 314.16(B) requires, then checks the total against you
Lawn & Garden
- Grass Seed CalculatorPick your grass type and the calculator uses its actual seeding rate. Overseeding an existing lawn takes roughly
- Sod CalculatorSod is sold in several different piece sizes depending on where you are. Pick the one your supplier uses.
- Fertilizer CalculatorEnter the first number from the bag and the nitrogen rate you want. This works backwards to the pounds of produc
- Lawn Area CalculatorReal lawns are not rectangles. Break yours into shapes, add them up, and subtract what is not grass.
- Plant Spacing CalculatorEnter the bed size and spacing. This gives both layouts, because staggered planting fits about 15% more plants i
- Raised Bed Soil CalculatorEnter the bed size and pick a mix. This splits the total into the components you actually have to buy.
- Garden Soil CalculatorFor in-ground beds and borders. The settlement allowance covers screened soil consolidating once it is spread an
- Compost CalculatorCompost goes on far thinner than mulch. A quarter-inch lawn topdressing is a different order of magnitude from a
- Yard Waste Bag CalculatorEnter the area and how deep the leaves are lying. The compression allowance matters — dry leaves pack down by ha
Calculators that show their working
Every calculator on ToolboxCalc prints the figure it relied on beside the answer — the density of the gravel, the yield printed on the concrete bag, the seeding rate for the grass you picked, the NEC table the wire resistance came from. A quantity you cannot check is a quantity you cannot trust, and the common mistakes in these jobs are not small: treating poured steps as one block per step under-orders concrete by three times at five steps, and spreading the product weight of a 24-0-4 fertilizer at a 10-10-10 rate puts down two and a half times the nitrogen.
One set of maths, tested
Each section’s arithmetic is a single module covered by a test suite checked against hand-worked references — volume shapes for building materials, unit conversion for lawn and garden products, and the NEC Chapter 9 tables for electrical work. The reference tables on each page are generated from the same code as the calculator above them, so a table can never disagree with the tool it sits under.
What these are not
Planning and purchasing estimates. Not structural engineering, not agronomic advice, and not an electrical design or inspection. Where a code, a label or a supplier’s specification applies to your job, it wins over anything here.