Construction & Engineering Calculators

Concrete, paint and tile estimators, NEC wire sizing and voltage drop, and air-conditioner BTU sizing.

BTU CalculatorSize a room air conditioner in BTU/h and tons from room area, ceiling height, sun exposure, occupants and kitchen use (ENERGY STAR guidance).
Concrete CalculatorCalculate concrete for slabs, footings and post holes in cubic yards, cubic metres and 40/60/80 lb bags, with a waste allowance. Free.
How Much Concrete for a 10x10 Slab?A 10×10 ft slab 4 inches thick needs 1.36 yd³ of concrete including 10% waste — 62 80 lb bags. Change the thickness below.
How Much Concrete for a 10x12 Slab?A 10×12 ft slab 4 inches thick needs 1.63 yd³ of concrete including 10% waste — 74 80 lb bags. Change the thickness below.
How Much Concrete for a 10x20 Slab?A 10×20 ft slab 4 inches thick needs 2.72 yd³ of concrete including 10% waste — 123 80 lb bags. Change the thickness below.
How Much Concrete for a 12x12 Slab?A 12×12 ft slab 4 inches thick needs 1.96 yd³ of concrete including 10% waste — 89 80 lb bags. Change the thickness below.
How Much Concrete for a 12x16 Slab?A 12×16 ft slab 4 inches thick needs 2.61 yd³ of concrete including 10% waste — 118 80 lb bags. Change the thickness below.
How Much Concrete for a 16x16 Slab?A 16×16 ft slab 4 inches thick needs 3.48 yd³ of concrete including 10% waste — 157 80 lb bags. Change the thickness below.
How Much Concrete for a 20x20 Slab?A 20×20 ft slab 4 inches thick needs 5.43 yd³ of concrete including 10% waste — 245 80 lb bags. Change the thickness below.
How Much Concrete for a 20x24 Slab?A 20×24 ft slab 4 inches thick needs 6.52 yd³ of concrete including 10% waste — 294 80 lb bags. Change the thickness below.
How Much Concrete for a 24x24 Slab?A 24×24 ft slab 4 inches thick needs 7.82 yd³ of concrete including 10% waste — 353 80 lb bags. Change the thickness below.
How Much Concrete for a 30x30 Slab?A 30×30 ft slab 4 inches thick needs 12.22 yd³ of concrete including 10% waste — 550 80 lb bags. Change the thickness below.
How Much Concrete for a 30x40 Slab?A 30×40 ft slab 4 inches thick needs 16.3 yd³ of concrete including 10% waste — 734 80 lb bags. Change the thickness below.
How Much Concrete for a 40x40 Slab?A 40×40 ft slab 4 inches thick needs 21.73 yd³ of concrete including 10% waste — 978 80 lb bags. Change the thickness below.
Paint CalculatorEstimate gallons or litres of paint for a room from its size, doors, windows and number of coats. Includes ceiling option and coverage per gallon.
Tile CalculatorCalculate how many tiles and boxes you need for a floor or wall from the area, tile size, grout joint and waste allowance. Free.
Voltage Drop CalculatorCalculate voltage drop and percentage for any wire size, current, voltage and distance, single or three-phase, using NEC Chapter 9 resistance.
Wire Size CalculatorFind the minimum copper or aluminum wire size (AWG/kcmil) for a load from NEC 310.16 ampacity and a voltage-drop limit. Single and three-phase.
Wire Size for 100 AmpsFor 100 A at 240 V over 100 ft, use at least 3 AWG copper (75 °C, ≤3% voltage drop). Shorter runs may allow a smaller size — check below.
Wire Size for 125 AmpsFor 125 A at 240 V over 100 ft, use at least 1 AWG copper (75 °C, ≤3% voltage drop). Shorter runs may allow a smaller size — check below.
Wire Size for 15 AmpsFor 15 A at 240 V over 100 ft, use at least 12 AWG copper (75 °C, ≤3% voltage drop). Shorter runs may allow a smaller size — check below.
Wire Size for 150 AmpsFor 150 A at 240 V over 100 ft, use at least 1/0 AWG copper (75 °C, ≤3% voltage drop). Shorter runs may allow a smaller size — check below.
Wire Size for 175 AmpsFor 175 A at 240 V over 100 ft, use at least 2/0 AWG copper (75 °C, ≤3% voltage drop). Shorter runs may allow a smaller size — check below.
Wire Size for 20 AmpsFor 20 A at 240 V over 100 ft, use at least 10 AWG copper (75 °C, ≤3% voltage drop). Shorter runs may allow a smaller size — check below.
Wire Size for 200 AmpsFor 200 A at 240 V over 100 ft, use at least 3/0 AWG copper (75 °C, ≤3% voltage drop). Shorter runs may allow a smaller size — check below.
Wire Size for 30 AmpsFor 30 A at 240 V over 100 ft, use at least 8 AWG copper (75 °C, ≤3% voltage drop). Shorter runs may allow a smaller size — check below.
Wire Size for 40 AmpsFor 40 A at 240 V over 100 ft, use at least 8 AWG copper (75 °C, ≤3% voltage drop). Shorter runs may allow a smaller size — check below.
Wire Size for 50 AmpsFor 50 A at 240 V over 100 ft, use at least 6 AWG copper (75 °C, ≤3% voltage drop). Shorter runs may allow a smaller size — check below.
Wire Size for 60 AmpsFor 60 A at 240 V over 100 ft, use at least 6 AWG copper (75 °C, ≤3% voltage drop). Shorter runs may allow a smaller size — check below.
Wire Size for 70 AmpsFor 70 A at 240 V over 100 ft, use at least 4 AWG copper (75 °C, ≤3% voltage drop). Shorter runs may allow a smaller size — check below.
Wire Size for 80 AmpsFor 80 A at 240 V over 100 ft, use at least 4 AWG copper (75 °C, ≤3% voltage drop). Shorter runs may allow a smaller size — check below.
Wire Size for 90 AmpsFor 90 A at 240 V over 100 ft, use at least 3 AWG copper (75 °C, ≤3% voltage drop). Shorter runs may allow a smaller size — check below.