I Made a Calculator for Comparing Free Cordless Power Tool and Battery Deals

Tool shoppers and deal-hunters will often come across “free with purchase” promotions, where you buy a cordless power tool product and receive a free bonus tool or battery.

I built an easy-to-use calculator that I hope you find handy for your deal-hunting and comparison efforts.

Prorated Value Calculator for ONE Free Bonus Item Deals

Simply enter the cost of the eligible tool or product you wish to buy, and the assigned value of the free bonus item, and this calculator will provide you with the prorated cost or return value for each.

For instance, if an eligible tool is $20, and it comes with a free bonus battery that is advertised as “saving” you $5, those are the numbers you would use here.

This calculator was a pain to code and get all the bugs out! If you find it helpful, please let me know in a comment!

If you are interested, visit ToolGuyd’s tool deals page, subscribe to our newsletter, or follow on social media.

You might also like our Amazon Deal Finder

Prorated Value Calculator for TWO Free Bonus Item Deals

If you want to compare more elaborate promotions, such as those involving 2 free cordless power tool or battery products, I built another calculator just for that:

Please note that these calculators and the explanation below only apply to (most) scenarios where the tool and free bonus item are considered separate purchases.

When a “free gift” is involved, the bonus item might be assigned a $0 value, and all items must be purchased or returned together.

How the Calculator is Meant to be Used

Many tool and home improvement retailers, such as Home Depot and Lowe’s, hold free bonus promotions featuring popular cordless power tool brands, such as Dewalt, Milwaukee, Makita, Ryobi, Ridgid, Craftsman, and Kobalt.

I posted about several cordless power tool deals the other day, and a reader commented about how one “free with purchase” promo offer was a better value than the others.

To compare deals, such as where multiple eligible tools or free bonus items are involved, you need to calculate the effective price of different components.

When you buy two identically-priced items in a “buy one, get one free” promotion, it’s easy to figure out you’re getting a 50% discount on both items. Figuring out the math for “free with purchase” cordless power tool deals is a little more complicated.

Calculating the prorated cost (or return value) for both the eligible tool and free bonus item in a promo, and repeating the process for different offers, can help one better compare values.

Let’s say one promotion features a cordless power tool kit for $299, and it’s eligible for a free bonus battery that’s valued at $99. The same cordless kit is on sale at a different retailer for $249. Which is the better bargain for the tool kit?

You could consider that you’re buying the cordless kit for $249 and getting the battery for $50, but that’s not exactly how retailers might calculate things.

I created these calculators as a way to compare the relative discounts provided by different promotions, although I understand that prorated costs and return values are sometimes used in other ways.

See Also: This is How the Home Depot Cordless Power Tool Deal “Hack” Works

The Math Explained

Here is how everything works. It’s good to know, even if just in case you find yourself at a store with a calculator but no internet service:

Tool = Cost of eligible item
Bonus = Value of free bonus item

Let’s say you buy something for $20 (Tool), and you get a free bonus worth $5 (Bonus).

You buy x, and get y for free. But, that’s not always how your purchase will be processed by a retailer.

If processed as two separate line items on a receipt or order, this order will usually be treated as if you are buying the tool for $20, and the bonus for $5, and receiving a $5 discount proportionally applied to both items.

$20 + $5 – $5 = $20.

You’re spending $20 and getting a tool and free bonus item.

However, although, the final cost is $20, not all of that goes towards the eligible purchase; part of the purchase price actually goes towards the free bonus, so as to assign both items prorated cost and return values.

Otherwise, couldn’t everyone return the purchased item and keep the free bonus for $0?

In other instances, the item and free bonus are considered a non-separable bundle that must be purchased and returned together. This post does not apply to deal bundles of that nature.

This is the discount, in decimal format, that the free bonus item applies to the order total (cost of eligible item + cost of free bonus):

So, with the $20 tool and $5 bonus, your purchase is treated as if you’re receiving a $5 discount on a $25 total. $5 over ($20 + $5) is 0.20 (or 20%).

You could multiply the discount by 100 to get the effective discount as a percentage, but we need it to remain in decimal format for the sake of our calculations.

Please note that the effective discount figure might be useful for comparative purposes, but should not be taken at face value. For the sake of “free bonus with purchase” promotions, retailers occasionally advertise or assign eligible tools, free bonus items, or both, at list prices or higher values than for items purchased separately. For example, a battery might be on sale for $99 separately, but valued at its regular price of $119 in a “free with purchase” promotion. The promotional value assigned by the retailer must be used for these calculations.

Multiply the savings ratio (Discount) by either item price to get their respective discounts in dollars.

I like to combine multiplication factors for simplicity:

So, the savings on the $20 item would be $20 x 0.20 = $4, and the savings on the $5 item would be $5 x 0.20 = $1. (If you add both savings together, that total is the assigned value of the free bonus item, or $4 + $1 = $5 in this example.)

Now, deduct this from the full price of the eligible item or assigned value of the free bonus item to calculate the prorated cost or return value for either item.

The prorated value of an item is the retail value, minus savings.

So, $20 – $4 = $16, which is the prorated value of the eligible tool, and $5 – $1 = $4, the prorated value of the free bonus item.

$16 + $4 = $20, the price of the eligible tool.

Things get just a little more complicated when dealing with more than 2 items.

Following is the math for when you buy an eligible product and receive 2 free bonus items with assigned retail or “savings” values.

Tool = Cost of eligible item
Bonuses= Total assigned value of all free bonus items

So let’s say you buy a tool for $40 and receive two separate free items, each valued at $5, for a total of $10 in free bonus items. The prorated value of the tool would be $40 – {($40 x $10} / ($40 + $10)} = $32. Each free item would have a prorated value of $5 – {($5 x $10} / ($40 + $10)} = $4 each. $32 + $4 + $4 = $40.

What if a cordless power tool kit is $249, one bonus item is $79, and another is $59? That’s where these calculators come in handy!

These calculators might not apply to all scenarios, and I make no guarantees as their accuracy, relevance, or suitability for any instances other than the aforementioned example. Use at your own risk.

Note: As with the equation listed above, this ONLY applies where a retailer might treat a “free bonus with purchase” promotion as the purchase of separate SKUs, with the free bonus value applied as a discount off the aggregate total.

Please let me know if you have any questions, or any tips or requests about how these calculators could be more useful!