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Building, electrical & garden calculators
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, gravel, sand, mulch and asphalt — in bags, yards and tons. 15 calculators
- Electrical Wire size, voltage drop, conduit and box fill, with the NEC tables built in. 7 calculators
- Lawn & Garden Grass seed, sod, fertilizer, soil and plant spacing for any lawn or bed. 8 calculators
- Everyday Math Percentages, discounts and tax, plus hours and minutes to decimal hours. 2 calculators
Building
- Concrete Slab CalculatorEnter the slab dimensions to get cubic yards, bag count by bag size, an estimated material cost,…
- Concrete Driveway CalculatorDriveways carry wheel loads, so they are thicker than a patio. Enter the dimensions for cubic ya…
- Concrete Footing CalculatorEnter the total run of footing, its width and thickness. Use the runs field if you have several …
- Post Hole Concrete CalculatorEnter the hole size and post dimension. This subtracts the volume the post occupies, which most …
- Concrete Steps CalculatorEnter the step width, count, rise and tread. This uses the real staircase volume, not one block …
- 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 man…
- Gravel CalculatorEnter the area and depth. You get loose cubic yards, tonnage at a real density, and a cost if yo…
- Gravel Driveway CalculatorA gravel driveway is built in lifts, not as one dump of stone. Enter the depth of each layer to …
- Paver Base CalculatorEnter the paver area and your base depth. This sizes the crushed stone only — bedding sand is a …
- 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 afte…
- 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 dens…
Reference charts
Electrical
- Voltage Drop CalculatorPick a wire size and the calculator looks up its resistance for you, then says whether the drop …
- Wire Size CalculatorEnter the load and the distance. This checks ampacity and voltage drop separately and tells you …
- Watts, Amps and Volts CalculatorConvert watts to amps or back, single or three phase, and get the breaker size including the con…
- Ohm's Law CalculatorEnter the two values you know, choose what to solve for, and the formula used is shown with the …
- Conduit Fill CalculatorPick the conduit and the conductors. This looks up both areas and applies the right fill limit f…
- Conduit Size CalculatorTell it what you are pulling and it finds the smallest conduit of that type which passes the fil…
- Box Fill CalculatorCounts conductors, devices, grounds and clamps the way NEC 314.16(B) requires, then checks the t…
Reference charts
- Wire Ampacity ChartNEC Table 310.16 for copper and aluminium, all three temperature columns, with the small-conduct…
- Wire Resistance ChartNEC Chapter 9 Table 8 resistance for copper and aluminium, which is the number every voltage-dro…
- Conduit Size ChartInternal area and usable fill for every common conduit type and size, from NEC Chapter 9 Table 4…
- Voltage Drop ChartHow far you can run each wire size at a given current before the 3% recommendation is exceeded.…
Lawn & Garden
- Grass Seed CalculatorPick your grass type and the calculator uses its actual seeding rate. Overseeding an existing la…
- Sod CalculatorSod is sold in several different piece sizes depending on where you are. Pick the one your suppl…
- Fertilizer CalculatorEnter the first number from the bag and the nitrogen rate you want. This works backwards to the …
- Lawn Area CalculatorReal lawns are not rectangles. Break yours into shapes, add them up, and subtract what is not gr…
- Plant Spacing CalculatorEnter the bed size and spacing. This gives both layouts, because staggered planting fits about 1…
- Garden Soil Calculator for Raised Beds, Planters and PotsPick a rectangular bed, a square planter or a round pot, enter its size and fill depth, and choo…
- Compost CalculatorCompost goes on far thinner than mulch, and the right depth depends on the job. Pick one for a s…
- Yard Waste Bag CalculatorEnter the area and how deep the leaves are lying. The compression allowance matters — dry leaves…
Reference charts
- Grass Seed Rate ChartEvery common lawn grass, its seeding rate new and overseeded, and when to sow it.…
- Fertilizer Rate ChartHow many pounds of product to spread for 1 lb of actual nitrogen, for every common bag analysis.…
- Plant Spacing ChartPlants per 100 square feet at every common spacing, both layouts, plus what spacing to use for w…
Everyday Math
No calculator matches that. Try a material (“gravel”), a job (“patio”) or a trade (“electrical”).
Why ToolboxCalc
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Shows its working
Every answer prints the figure it relied on — the density of the gravel, the yield on the concrete bag, the seeding rate for your grass, the NEC table behind the wire size. The common mistakes in these jobs are not small: treating poured steps as one block per step under-orders concrete three times over at five steps.
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One set of tested maths
Each section’s arithmetic is a single module checked against hand-worked references by a test suite. The reference tables on every page are generated from the same code as the calculator above them, so a table can never disagree with the tool it sits under.
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Honest about its limits
These are planning and purchasing estimates — not structural engineering, agronomic advice, or an electrical design or inspection. Where a code, a product label or your supplier’s specification applies to the job, it wins over anything here.