Number and slider
Two types collect a number: Number, which the customer types, and Slider, which they drag between two bounds.
Both are available on every plan, including Free, and formula pricing is the reason they exist — a number the customer supplies is the natural input to price per centimetre.
Their pricing rules are not identical, and the difference is deliberate:
| Number | Slider | |
|---|---|---|
| Flat fee | Yes | No |
| Percentage of product price | Yes | Yes |
| Formula | Yes | Yes |
| Quantity tiers | Yes | Yes |
| Per character | No | No |
A slider is answered from the moment it renders — the customer cannot decline it. A flat fee on a field nobody can leave blank is not an add-on, it is an unconditional surcharge nobody opted into, so it is not offered. What remains prices the value the customer chose, which is the only thing a slider expresses.
Neither type offers per character: billing by the digit count of a number is not something a merchant means to do, and offering it invites a mis-click that overcharges every order.
Number
Section titled “Number”A typed value, with optional minimum, maximum and step. It can be genuinely empty: a customer who types nothing has not answered.
Use it when “no answer” means something different from “the default value”.
Slider
Section titled “Slider”A value dragged between two bounds. A slider always has a position, so it always has an answer — the customer can add to cart without touching it and still produce a value.
Use it when any value in the range is acceptable and you want the customer to explore it. Do not use it for something that should be a deliberate decision, because an untouched slider still submits its starting value.
Setting bounds
Section titled “Setting bounds”Set both bounds on every numeric option. An unbounded number field accepts 999999, and a formula multiplying that by a per-unit price produces a cart line neither of you intended.
The step controls what values are allowed. A step of 0.5 on a length in centimetres allows 12.5 but not 12.3.
Worked example: price per centimetre
Section titled “Worked example: price per centimetre”A Length (cm) number option, bounded 10–200, with a formula rule:
length_cm * 0.40| Customer enters | Added |
|---|---|
10 |
£4.00 |
55 |
£22.00 |
200 |
£80.00 |
The variable name comes from the option’s label, lowercased with non-letters turned into underscores — Length (cm) becomes length_cm. See Formula.