*Edit: Updated August 2018 with more examples and links to relevant topics.*

**Summary:**To solve for equilibrium price and quantity you should perform the following steps:

1) Solve for the demand function and the supply function in terms of Q (quantity).

2) Set Qs (quantity supplied) equal to Qd (quantity demanded). The equations will be in terms of price (P)

3) Solve for P, this is going to be your equilibrium Price for the problem.

4) Plug your equilibrium price into either your demand or supply function (or both--but most times it will be easier to plug into supply) and solve for Q, which will give you equilibrium quantity.

When solving for equilibrium price and quantity, you need to have a demand function, and a supply function. Sometimes you will be given an inverse demand function (ie. P = 5 –Q) in this case you need to solve for Q as a function of P. Once you have both your supply and demand function, you simply need to set quantity demanded equal to quantity supplied, and solve.

This is best explained by using an example...

Suppose your monthly quantity demand function for a product is Qd = 10,000-80P, and your monthly quantity supply function for a product is Qs=20P, then we need to follow the first step outlined above and set Qd=Qs and solve for price.

1) Qd=Qs which is also equal to--

2) 10,000 – 80P = 20P

We then must add 80P to both sides, then divide by 100 to get:

100 = P

(we got the above by adding 80P to both sides which gave us 10,000=100P, then divided both sides by 100 to get 100 = P)

(we got the above by adding 80P to both sides which gave us 10,000=100P, then divided both sides by 100 to get 100 = P)

Which is our equilibrium price. Now to find equilibrium quantity we can plug our equilibrium price (100) into either our demand or supply function. If we plug it into our demand function we get:

Qd= 10,000 – 80*100 = 2,000

We get 2,000 because 80*100 is 8,000... and 10,000 minus 8,000 is 2,000.

We get 2,000 because 80*100 is 8,000... and 10,000 minus 8,000 is 2,000.

If we plug it into our supply function we get:

Qs = 20*100 = 2,000

Luckily, our quantity supplied is equal to our quantity demanded so we know that we did it right. It can also help to look at the graphs associated with market equilibrium if you are having problems developing the intuition for the math.

So the steps are:

1) Get functions solved for Qs (quantity supplied) and Qd (quantity demanded).

2) Set Qs equal to Qd

3) Solve for P (equilibrium price)

4) Plug your P back into your Qs and Qd functions to get equilibrium quantity

*What’s going on behind the scenes?*

The reason we set Qs equal to Qd is because we know that in equilibrium they must be equal. Since supply and demand will only cross at one point, we know that when Qs = Qd that we are at equilibrium. We can use this information to solve for equilibrium price even though we don’t know what Qd and Qs are! Once we do have equilibrium price, we can use this information to back out what Qs and Qd are.

**Another example:**

Suppose that demand is given by the equation QD=500 – 50P, where QD is quantity demanded, and P is the price of the good. Supply is described by the equation QS= 50 + 25P where QS is quantity supplied. What is the equilibrium price and quantity?

So here we get:

Qd=Qs=500-50P=50+25P

or (subtract 50 from both sides, and add 50P to both sides to get)

450=75P

divide both sides by 75 to get P = 6.

Plug P = 6 into both quantity functions:

500-50(6) = 200

and

50+25(6) = 200

So we know that equilibrium price is 6, and equilibrium quantity is 200.

Related lessons: Sometimes you will what to solve for equilibrium after a shift in either supply or demand. Other times you will want to calculate a change in equilibrium after an income change. Sometimes people will refer to the equilibrium price and quantity formula, but that is a bit of a misnomer. The formula that you use to calculate equilibrium price and quantity is Qd=Qs and then following the steps that are outlined above.

This helped me so well! Thanks for using such a clear way to explain things

ReplyDeleteThank u so much :)

ReplyDeleteThanks

ReplyDeleteExcellent!! Thank you for making this easy to follow example at a pace I could follow. Thank you!!!

ReplyDeleteYes, this was an awesome lesson. Straight forward explanations and good examples. Thank you!

ReplyDeleteThis was an awesome way for me to finally get the formula and how to use it and it's purpose. Now I have a question, how would I explain it in a graph?

ReplyDeletePls help i got supply equation Qs=-100➕10p calculate price of supply given price change from 20 to 35

DeleteThanks a lot!

ReplyDeletenice lecture

ReplyDeleteThanks a lot. This is so clearly illustrated. But now my two questions are : 1. What would the quantities demanded and supplied be (Diagrammatically or otherwise)? [Traci Gonzalez above is on point]. 2. What would happen in the markets?

ReplyDeleteThis article solved my problem, i appreciate for sharing the solution. Commodity tips

ReplyDeletehelp!!

ReplyDeleteconsider a competitive market for a good where the demand is determined by the demand function: O=6-Qd and supply curve is determined by the supply function: P=2+Qs.

what is the quantity demanded of the good when the price level is: P=$2?

what is the quantity supplied of the good when the price level is: P=$2?

what is the equilibrium quantity level for the good in the competitive market?

what is the equilibrium price level for the good in the competitive market?

what is tge consumer and producers surplus in the competitive narket?

what is the level surplus in the competitive market?

That was a great mathematics! I am already noted this in my hand note. You know I am a student of mathematics. By the way, the post is really impressive. Thank you so much and I appreciate that kind of work. mathematics typing

ReplyDeletePlease help how to solve this Qs=28000+35p and Qd=80000-25p ,Qd=60000-10p , Qd=40000-6p. How do I determine the equilibrium market price and quantity

ReplyDeleteI have P= 100-.01QD

ReplyDeleteP= 10 + .01QS

Calculate equilibrium price and quantity

I am so much excited after reading equilibrium price and quantity. Your math is very much innovative and much helpful for any industry as well as for person.Harrison Ford Jacket

ReplyDeleteThankyou so much this help in my preparation for the exam❤

ReplyDeleteWow, this site is awesome guys!

ReplyDeleteHey this helped me a lot. Thanks admin

ReplyDeleteAwesome...nice lecture

ReplyDeleteFind the equilibrium price P_e and quantity Q_efor each of the following marketS using (1) equations and (2) graphs:

ReplyDeleteSupply: P=1/4 Q+2 Demand: P=-3/4 Q+22

I think this is a really good article. You make this information interesting and engaging. I guess I am not only one having all the enjoyment right here! Lara Croft Tomb Raider Jacket

ReplyDeleteI have Pd=450-2Qd;Ps=100+5Qs

ReplyDelete(i)Calculate the equilibrium quantity and price

(ii)If the government provides a subsidy of $70 per unit sold, find the new equilibrium quantity and price

It has been helpful thank you

ReplyDeleteand im also stuck with this one

Qd=15-p

Qs=3-P

the requirement is to solve the equilibrium qty and Equilibrium pricw

P=1600-80q

ReplyDeleteS there missing i cant solve this

Demand Q= 15 P

ReplyDeleteSupply P=3

Assist to solve for equilibrium quantity and equilibrium price

ReplyDeleteGiven marginal cost is $5, 20 trips per day and demand function is 1200-peP. Calculate the equilibrium price and equilibrium quantity

ReplyDeleteKeep posting the good work. Some really helpful information in there. Bookmarked. Nice to see your site. Thanks! learning videos

ReplyDeleteBack to general equilibrium. In the.will use a model to describe the ... of consumer and producers. a vector of input prices, and b is. prices and quantities. For welfare. Motorcycle Jacket

ReplyDeletesupply is low demand will be high If demand is high prices are high. If demand is low supply is high. If demand. Outfit

ReplyDeleteThanks for the good free lesson!

ReplyDeleteAm really grateful for this lesson.It has helped me a lot.

ReplyDeletePlease help solve this for me. If quantity demand = 50-1/3p and quantity supplied is = 10+2/4p, what is the equillibrum price and quantity

ReplyDelete...Thanks ....its now easy for me

ReplyDeleteThanks alot

ReplyDeleteHelp me solve this, the demand and supply functions of a good are given by

ReplyDeleteP= -Qd +125

2P= 3Qs +30

Deteimine the equilibrium price and quantity. Determine the effect tax, if tax of £5 per unit on good.