Price Comparison Calculator
Which option is cheaper per unit?
Compare price per unit across two products with this price comparison calculator to find the cheaper option by package size or quantity.
What this tool does
This calculator compares the per-unit cost of two product options to show which represents better value. Enter the price and quantity for option A and option B. The calculator divides each total price by its quantity to compute the cost per unit, then displays both results side by side along with which option has the lower per-unit cost and by how much. This approach isolates price efficiency from pack size, making it straightforward to compare products sold in different quantities—larger packs don't automatically mean better value. The result is calculated on the figures you enter and doesn't account for factors like quality differences, shelf life, or usage patterns. Use this for everyday shopping comparisons or any scenario where items are priced differently by volume or count.
Enter Values
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Formula Used
Spotted something off?
Calculations or display — let us know.
Disclaimer
Results are estimates for educational purposes only. They do not constitute financial advice. Consult a qualified professional before making financial decisions.
4.50 for 500g vs 7.20 for 900g: 0.009/g vs 0.008/g — bigger pack is 11% cheaper per gram. Reveals hidden pricing tricks. Common example: some 'bulk' sizes are actually per-unit more expensive than standard size.
Quick example
With option a price of 4.5 and option a quantity of 500 (plus option b price of 7.2 and option b quantity of 900), the result is Option B. Change any figure and watch the output shift — it's often more useful to see the pattern than to memorise the formula.
Which inputs matter most
You enter Option A Price, Option A Quantity, Option B Price, and Option B Quantity. Two inputs usually tip the answer one way or the other. Identify which ones matter most by flipping each value past a round threshold and watching whether the option with the lower calculated total changes.
What's happening under the hood
Price divided by quantity for each option. The formula is listed in full below. If the number looks off, you can retrace the calculation by hand — that's the point of showing the working.
What the bill doesn't show
Standing charges, discounts, and usage tiers all blur the effective rate. The calculation here backs out the total so you're comparing apples to apples across providers, regardless of how each one packages the price.
What this doesn't capture
Usage varies month-to-month; tariffs change; discounts come and go. The figure here is a clean baseline — your actual annual bill will fluctuate around it. Use the calculation to benchmark providers, not as a prediction of a specific bill.
Where to go next
This calculation rarely sits alone in a planning exercise. If you're running these numbers, you'll probably also want the bulk buy savings calculator, the break even price calculator, and the price per unit calculator — each one answers a different question in the same territory. Treating them as a set rather than in isolation usually produces a more honest picture.
When comparing £4.5 for 500 units against £7.2 for 900 units, Option B offers the lower per-unit cost.
Inputs
This example uses typical values for illustration. Adjust the inputs above to match a specific situation and see how the result changes.
Sources & Methodology
Methodology
This calculator computes the unit price for each option by dividing the total price by the quantity supplied. It then displays both unit prices side by side, allowing direct comparison. The model assumes that price and quantity are both positive values and treats them as fixed inputs with no hidden costs or volume discounts applied. It does not account for variations in product quality, packaging differences, shelf life, or any additional fees that may apply at purchase or delivery. The result represents a straightforward per-unit cost and should be combined with other factors—such as quality, availability, or actual usage patterns—to inform purchasing decisions.
References
Frequently Asked Questions
Is cheaper always better?
Why do shops not show unit prices?
Bulk vs single — rule of thumb?
Same units required?
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