Finance
How to Calculate Payback Period in Excel
The payback period is how long an investment takes to earn back its cost. It is one of…
Guides & Formulas
In-depth guides, formulas, and how-tos for engineering, trades, and everyday calculations. Learn the method, then use the matching free calculator.
Percentage
How to Calculate Percentage of Marks: Formula, Examples & Calculator
Your percentage of marks shows how much of the total you scored, on a scale of 100. Schools,…
Percentage
How to Decrease a Number by a Percentage (and Find Loss Percentage)
Price cuts, falling sales, and business losses all come down to one skill: taking a percentage off a…
Percentage
How to Calculate Discount Percentage
A sale tag might show the old price and the new price but not the discount, or the…
Math
How to Find Diameter From Circumference Without Radius
You can wrap a tape around a pipe, a tree, or a column far more easily than you…
Math
How to Calculate Distance Formula (Distance Between Two Points)
The distance formula measures the straight-line distance between two points on a graph. It is the Pythagorean theorem…
Physics
Heat Transfer Formula: Q = mcΔT Explained
Heating a material takes energy, and the equation for heat transfer tells you how much. This guide covers…
HVAC
How to Calculate Relative Humidity (RH Formula)
Relative humidity is the amount of water vapour in the air compared with the most it could hold…
Electrical
kVA to kW: Formula and How to Convert
kVA is apparent power and kW is real power. Converting kVA into kW is a common job when…
Electrical
Amps to kW Formula for Single and Three Phase
Converting amperes to kilowatts turns a breaker or clamp meter reading into the real power a load draws.…
Electrical
Volts, Amps, and Watts: The Power Formula (P = V × I)
Volts, amps, and watts are tied together by one relationship. Once you know any two, the third follows.…
HVAC
Duct Sizing Chart: How to Size Ductwork by CFM
A duct has to carry a set airflow without the air moving so fast that it whistles or…
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