Law of Demand Calculator

The Law of Demand Calculator helps you estimate how changes in price affect the quantity demanded of a product or service. According to the law of demand, when price rises, demand falls, and when price falls, demand rises — assuming all else remains constant.

This calculator is especially useful for businesses, economists, and students analyzing market behavior.

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🔹 Formula

The percentage change in demand can be estimated with: Elasticity of Demand (Ed)=% ΔQ% ΔP\text{Elasticity of Demand (Ed)} = \frac{\%\ \Delta Q}{\%\ \Delta P}Elasticity of Demand (Ed)=% ΔP% ΔQ​

Where:

• % ΔQ\%\ \Delta Q% ΔQ = % change in quantity demanded
• % ΔP\%\ \Delta P% ΔP = % change in price

Once elasticity (Ed) is known, you can estimate demand shift: Qnew=Qold×(1+(Ed×% ΔP))Q_{new} = Q_{old} \times \left(1 + (Ed \times \%\ \Delta P)\right)Qnew​=Qold​×(1+(Ed×% ΔP))

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🔹 How to Use the Calculator

1. Enter the initial price (P1).
2. Enter the new price (P2).
3. Enter the initial quantity demanded (Q1).
4. Enter the price elasticity of demand (Ed) (if known).
5. Click calculate → Get the new demand (Q2) and demand change %.

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🔹 Example 1 – Elastic Demand

• Initial price (P1) = $10
• New price (P2) = $8
• Initial demand (Q1) = 1,000 units
• Elasticity (Ed) = -1.5

Step 1: % Change in Price 8−1010×100=−20%\frac{8 – 10}{10} \times 100 = -20\%108−10​×100=−20%

Step 2: % Change in Demand −1.5×(−20%)=+30%-1.5 \times (-20\%) = +30\%−1.5×(−20%)=+30%

Step 3: New Demand Q2=1000×(1+0.30)=1,300Q2 = 1000 \times (1 + 0.30) = 1,300Q2=1000×(1+0.30)=1,300

👉 Demand increases to 1,300 units.

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🔹 Example 2 – Inelastic Demand

• Initial price (P1) = $5
• New price (P2) = $6
• Initial demand (Q1) = 500 units
• Elasticity (Ed) = -0.4

Step 1: % Change in Price 6−55×100=+20%\frac{6 – 5}{5} \times 100 = +20\%56−5​×100=+20%

Step 2: % Change in Demand −0.4×20%=−8%-0.4 \times 20\% = -8\%−0.4×20%=−8%

Step 3: New Demand Q2=500×(1−0.08)=460Q2 = 500 \times (1 – 0.08) = 460Q2=500×(1−0.08)=460

👉 Demand decreases slightly to 460 units.

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🔹 Why Use a Law of Demand Calculator?

✔️ Predict customer behavior with price changes
✔️ Test elasticity of your product/service
✔️ Support pricing decisions for businesses
✔️ Understand consumer response for economics projects
✔️ Estimate sales changes before applying discounts or increases

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🔹 Practical Applications

• Retail & e-commerce → check how discounts affect sales
• Economics students → study elasticity concepts
• Businesses → forecast revenue impacts of pricing
• Government & policy → evaluate effect of taxes on consumption
• Investors → analyze industry demand sensitivity

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🔹 FAQ – Law of Demand Calculator

1. What is the law of demand?
It states that as price rises, demand falls, and as price falls, demand rises, all else equal.

2. What is elasticity?
Elasticity measures how sensitive demand is to price changes.

3. What if elasticity = 0?
Demand is perfectly inelastic — it doesn’t change with price.

4. What if elasticity = -∞?
Perfectly elastic — demand drops to zero if price increases at all.

5. What’s the difference between elastic and inelastic demand?

• Elastic (|Ed| > 1): demand changes a lot with price.
• Inelastic (|Ed| < 1): demand changes little.

6. Can this work for services as well?
Yes — applies to both products and services.

7. Does this include income effects?
No — it assumes other factors stay constant (ceteris paribus).

8. Can it be used for luxury goods?
Yes — elasticity is often high for luxury items.

9. What if elasticity is unknown?
You can input estimated values from studies or experiments.

10. Is this useful for revenue forecasting?
Yes — by combining demand shifts with price changes.

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🔹 Conclusion

The Law of Demand Calculator is a powerful tool for understanding how price changes affect consumer demand. By factoring in elasticity, businesses, policymakers, and students can predict shifts in quantity demanded and make smarter decisions.