Building
Building calculators that get the maths right
How to describe prices, tiers, discounts and add-ons.
Give the calculator every number it needs in the description. Widgev does not invent prices; if one is missing it uses a clearly labelled example.
Describe the inputs
Say what the visitor changes: "seats slider from 1 to 200", "a plan select with Starter, Pro and Business", "a yearly billing toggle".
Describe the rules
- Per-unit: "Starter is $9 per seat, Pro $19, Business $39" - Discounts: "20% off when billed yearly" - Add-ons: "an extra $50 per month for priority support" - Tiers: "the first 10 seats are $12, seats above 10 are $9"
Describe the outputs
"Show the monthly total and the yearly total" or "show total savings per year".
Check it
Move the sliders in the preview and check a couple of values by hand. Then change a number with words ("make Pro $24") and check again.
Related
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