Discount Calculator

How to Use the Discount Calculator

This calculator handles five discount scenarios: percent-off, fixed-amount-off, stacked sequential discounts, reverse-calculating the original price from a sale price, and finding the discount percentage from two prices. All calculations use exact decimal arithmetic.

Calculation Modes

Percent Off

Enter the original price and a percentage discount. The calculator computes the final price.

Formula: Final = Original × (1 − Percent / 100)

Example: A $120 item with 25% off

• Original Price: 120
• Discount: 25
• Final Price: 90

Example: A $500 item with 15% off

• Original Price: 500
• Discount: 15
• Final Price: 425

Fixed Off

Enter the original price and a fixed dollar discount. The calculator computes the final price.

Formula: Final = Original − Amount

Example: A $150 item with $40 off

• Original Price: 150
• Discount Amount: 40
• Final Price: 110

Example: A $99 item with $20 off

• Original Price: 99
• Discount Amount: 20
• Final Price: 79

Stacked

Apply up to three discounts sequentially. Each discount is calculated on the price remaining after the previous discount. Each discount can be either a percentage (%) or a fixed amount ($).

Example: $200 with 20% off then $15 off

• Original Price: 200
• Discount 1: 20% off
• Discount 2: $15 off
• Step 1: 20% off the original $200 = $40 discount, new price: 160
• Step 2: $15 off the remaining $160 = $15 discount, new price: 145
• Final Price: 145
• Total Savings: 55
• Effective Discount: 27.5

Example: $500 with 10% off, then 5% off, then $25 off

• Original Price: 500
• Discount 1: 10% off
• Discount 2: 5% off
• Discount 3: $25 off
• Step 1: 10% off the original $500 = $50 discount, new price: 450
• Step 2: 5% off the remaining $450 = $22.5 discount, new price: 427.5
• Step 3: $25 off the remaining $427.5 = $25 discount, new price: 402.5
• Final Price: 402.5
• Total Savings: 97.5
• Effective Discount: 19.5

After calculating, a discount breakdown table shows each step with the description, discount amount (in red), and running price. The footer shows total savings with the effective percentage and the final price.

Find Original

Work backwards from a sale price and known discount percentage to find the original price before the discount was applied.

Formula: Original = Sale / (1 − Percent / 100)

Example: You paid $80 for an item that was 20% off

• Sale Price: 80
• Discount Applied: 20
• Original Price: 100

Example: Sale price $135 with 10% discount

• Sale Price: 135
• Discount Applied: 10
• Original Price: 150

Find %

Calculate the discount percentage when you know the original price and the final price.

Formula: Percent = ((Original − Final) / Original) × 100

Example: Original $200, final $150

• Original Price: 200
• Final Price: 150
• Discount: 25

Example: Original $80, final $68

• Original Price: 80
• Final Price: 68
• Discount: 15

Precision and Notation Settings

Use the settings bar above the tabs to control how results display:

• Decimal places: Adjust from 0 to 16 decimal places (default is 8)
• Notation: Switch between auto, fixed, exponential, and engineering notation (default is auto)

Your decimal places and notation settings save to your browser automatically. When you return to this calculator, your last chosen format loads without needing to adjust it again.

Common Use Cases

Shopping Sale

A jacket is $89.99 with 30% off:

1. Switch to Percent Off
2. Enter 89.99 as Original Price
3. Enter 30 as Discount
4. Final Price: 62.993

Coupon Plus Store Discount

An item costs $250 with a store-wide 15% off plus a $20 coupon:

1. Switch to Stacked
2. Enter 250 as Original Price
3. Discount 1: 15 with type %
4. Discount 2: 20 with type $
5. Final Price: 192.5

Verifying a Discount Claim

A store claims "50% off" but the sale price is $45 and you suspect the original was $80:

1. Switch to Find %
2. Enter 80 as Original Price
3. Enter 45 as Final Price
4. Discount: 43.75 (less than claimed)

Pricing Items for a Sale

You want to sell an item for $60 after applying a 20% discount:

1. Switch to Find Original
2. Enter 60 as Sale Price
3. Enter 20 as Discount Applied
4. Original Price: 75 (list at $75)

Multiple Promotions

A $400 item has a members-only 10% discount plus a seasonal 15% discount:

1. Switch to Stacked
2. Enter 400 as Original Price
3. Discount 1: 10 with type %
4. Discount 2: 15 with type %
5. Final Price: 306 (not $280; stacked discounts compound)

Tips for Accurate Calculations

1. Stacked discounts are sequential: Each applies to the price remaining after the previous one
2. Select the correct discount type: In stacked mode, choose % or $ for each discount
3. Fixed discounts cannot exceed the price: The calculator rejects a fixed discount larger than the current price
4. Find Original requires a percentage: Enter the discount as a percent, not a fixed amount
5. Compare fixed and percent discounts mentally: A $20 discount on $100 equals 20%, but on $80 it equals 25%
6. Order matters for stacked discounts: Mixing percent and fixed in different orders produces different results

Troubleshooting

Required

This appears when a field is left empty. Enter a value in all required fields before calculating.

Original price must be positive

Enter a value greater than 0 for the original price. Zero and negative prices are rejected.

Discount percent cannot be negative

Enter zero or a positive percentage. Negative discounts are not valid.

Discount amount cannot be negative

Enter zero or a positive amount. Negative discounts are not valid.

Discount must be a non-negative number

In Stacked mode, each discount value must be zero or positive.

Select a discount type

In Stacked mode, choose % or $ for each discount you enter.

Sale price must be positive

Enter a value greater than 0 for the sale price.

Final price cannot be negative

Enter zero or a positive value for the final price.

Final price must be less than original price

In Find % mode, the final price must be lower than the original. If they are equal, no discount exists.

Discount cannot be greater than or equal to price

In Fixed Off mode, the discount amount must be less than the original price.

Discount must be between 0% and 100%

In Find Original mode, enter a percentage greater than 0 and less than 100. A 100% discount would make the original price infinite.

Discount cannot exceed current price

In Stacked mode, a fixed discount cannot be larger than the price at that step.

Breakdown table not appearing

The table only renders after a successful Stacked calculation with at least one valid discount. Check that all required fields are filled and the discount type is selected.