The phrase "a quantity equal to" is correct and usable in written English.
It can be used in mathematical or scientific contexts to describe a specific amount that matches another amount.
Example: "The formula states that the area of a circle is a quantity equal to π times the radius squared."
Alternatives: "an amount that matches" or "a value equivalent to".
We analysed the climate summit's potential impact, finding that these 29 collaborative commitments could close the 2020 emissions gap by one-fifth, a quantity equal to India's annual emissions in 2012.
Some 170,000 megawatts of new power plant capacity is in development in the U.S., a quantity equal to 23% of existing capacity.
In those cases, estimate of the frame boundary may be shifted by a quantity equal to the delay of the dominant path.
To divide the colonies between imperialists, a quantity equal to (NC_n ) from the colonies was randomly selected and allocated to imperialists.
To ensure a balanced comparison, the most highly significant DEGs were selected in a quantity equal to the number of genes.
According to the theory, the CV of a quantity equals to the standard deviation of the same quantity after logarithmic transformation, that is where σ(x) represents the standard deviation of x and ln(x) is the natural logarithmic function.
Momentum, a directed quantity equal to the mass of a body multiplied by its velocity or to the total mass of two or more bodies multiplied by the velocity of their centre of mass, is conserved when, and only when, no external force acts.
In 1883 Osborne Reynolds, a British engineer and physicist, demonstrated that the transition from laminar to turbulent flow in a pipe depends upon the value of a mathematical quantity equal to the average velocity of flow times the diameter of the tube times the mass density of the fluid divided by its absolute viscosity.
Several high capacity tanks have been built and tested up to a hydrogen quantity equal to 0.6 kg.
A small quantity, equal to 1/10 of the smallest measurable sample concentration, was artificially added to the hCG-sLHCGR values to avoid zeros in the log-transformation.
From this Faraday concluded that the total charge of the system was an invariable quantity equal to the initial charge of the ball.
