Equilibrium Price Calculator

Give this the four numbers that describe a linear supply curve and a linear demand curve and it returns the price where the two cross, the quantity traded there, and the consumer and producer surplus as areas under each curve rather than as assumed triangles. A second form adds a per-unit tax and splits the burden between buyers and sellers, showing that the split does not depend on who hands the money over; a third imposes a price floor or a price ceiling and reports the surplus or the shortage it creates. Every intervention reports a deadweight loss that, added to the surpluses and any tax revenue, comes back to the total the free market had. The chart draws both curves with the surplus areas shaded, because equilibrium is a crossing before it is a number.