> ## Documentation Index > Fetch the complete documentation index at: https://zenskar.com/docs/llms.txt > Use this file to discover all available pages before exploring further. # Per-unit pricing model ## Per-unit pricing model The per-unit pricing model is one of the [pricing models](/docs/20260301/pricing-models/concepts/pricing-models). This page explains how it calculates the amount of a pricing preset. ### Map of concepts | Concept | Details | | - | - | | [Per-unit pricing model](#per-unit-pricing-model-the-same-price-for-every-unit) | The per-unit pricing model multiplies the quantity of each period by the price per unit. | | [Point-in-time products](#point-in-time-products-one-charge-for-each-unit) | If the product is a point-in-time product, each unit costs the price per unit once. | | [Period-of-time products](#period-of-time-products-a-price-for-each-pricing-period) | If the product is a period-of-time product, the price per unit covers one pricing period. Zenskar converts it to the length of each billing period. | | [Partial periods](#partial-periods) | If a billing period is only partly covered, the line item decides whether the amount is prorated. | | [On-demand quantities](#on-demand-quantities-on-period-of-time-products) | If a period-of-time product uses the on-demand quantity strategy, each unit costs the full price per unit in the billing period in which it occurs. | | [Per-unit pricing model on a line item](#per-unit-pricing-model-on-a-line-item) | A line item can override the price per unit and the pricing period. | ### Related modules The following modules use the per-unit pricing model: | Module | Details | | - | - | | [Products](/docs/20260301/product-modules/products/concepts/products#pricing-presets-how-you-charge) | A pricing preset can use the per-unit pricing model. For the steps, see [Set up the per-unit pricing model](/docs/20260301/product-modules/products/how-to-guides/pricing-presets#set-up-the-per-unit-pricing-model). For the fields, see [Per-unit fields](/docs/20260301/product-modules/products/reference/pricing-presets#per-unit-fields). | | [Contracts](/docs/20260301/product-modules/contracts/concepts/line-items/pricing) | A line item calculates its charges with the per-unit pricing model of its pricing preset, and can override its values. The billing of the line item decides the billing periods. See [Line item: billing](/docs/20260301/product-modules/contracts/concepts/line-items/billing). | ## Per-unit pricing model: the same price for every unit The **per-unit pricing model** is the [pricing model](/docs/20260301/product-modules/products/glossary#pricing-model) that charges the same price for every unit. The per-unit pricing model has one value: the price per unit, in **Price per unit**. For each period, the amount is the quantity of that period multiplied by the price per unit: ```text theme={null} amount = quantity × price per unit ``` The amount grows in direct proportion to the quantity. Ten units always cost ten times as much as one unit, so the per-unit pricing model gives no discount for a larger quantity. For prices that change with the quantity, see [Pricing models](/docs/20260301/pricing-models/concepts/pricing-models). The price per unit can be 0 or more, with up to 10 decimal places. A price per unit of 0 makes the units free. A price per unit of \$0.0025 for each API call gives the following amounts: | Quantity | Amount | | - | - | | 400 | \$1.00 | | 10,000 | \$25.00 | | 1,000,000 | \$2,500.00 | Zenskar keeps the full precision of the price per unit during the calculation. It rounds the amount to the currency at the end of the calculation of the [line item](/docs/20260301/product-modules/contracts/glossary#line-item). What a period is depends on the [product type](/docs/20260301/product-modules/products/glossary#product-type). See [Point-in-time products](#point-in-time-products-one-charge-for-each-unit) and [Period-of-time products](#period-of-time-products-a-price-for-each-pricing-period). ## Point-in-time products: one charge for each unit For a [point-in-time product](/docs/20260301/product-modules/products/glossary#point-in-time-product-type), the price per unit is the price of one unit, with no period attached. For example, \$0.01 per SMS. A pricing preset of a point-in-time product has no [pricing period](/docs/20260301/product-modules/products/glossary#pricing-period). Zenskar charges each unit once, in the [billing period](/docs/20260301/product-modules/contracts/glossary#billing-period) in which the line item counts it. The amount of each billing period is the quantity of that billing period multiplied by the price per unit. Billing periods do not affect each other: the price per unit stays the same, however many units earlier billing periods had. A pricing preset at \$0.01 per SMS, with metered usage and monthly billing, gives the following amounts: | Billing period | Quantity | Amount | | - | - | - | | January | 12,000 | \$120.00 | | February | 9,500 | \$95.00 | | March | 0 | \$0.00 | The line item decides which units fall in which billing period, through its [quantity strategy](/docs/20260301/product-modules/products/glossary#quantity-strategy) and its billing. See [Line item: quantity](/docs/20260301/product-modules/contracts/concepts/line-items/quantity) and [Line item: billing](/docs/20260301/product-modules/contracts/concepts/line-items/billing). ## Period-of-time products: a price for each pricing period For a [period-of-time product](/docs/20260301/product-modules/products/glossary#period-of-time-product-type), the price per unit covers one pricing period. For example, \$20 per seat per month. Every pricing preset of a period-of-time product has a pricing period, and the pricing period is monthly by default. The billing periods of a line item do not have to match the pricing period. Zenskar converts the price to the length of each billing period with the period ratio. The **period ratio** is the length of a billing period divided by the length of its pricing period. For each billing period, the amount is: ```text theme={null} amount = quantity × price per unit × period ratio ``` The following amounts are for 10 seats: | Price per unit | Billing period | Period ratio | Amount for each billing period | | - | - | - | - | | \$20 per month | Month | 1 | \$200.00 | | \$30 per quarter | Month | 1/3 | \$100.00 | | \$20 per month | Quarter | 3 | \$600.00 | | \$240 per year | Quarter | 1/4 | \$600.00 | The period ratio counts calendar months, not days. A monthly billing period of a quarterly price has a period ratio of 1/3 in February and in March alike, so both months cost the same. A pricing period is always a whole number of months or years. The pricing period and the billing period must align: one must be a whole multiple of the other. See [Line item: billing](/docs/20260301/product-modules/contracts/concepts/line-items/billing). This section describes billing periods that the line item covers in full, with the [recurring quantity strategy](/docs/20260301/product-modules/products/glossary#recurring-quantity-strategy). For billing periods that the line item covers only in part, see [Partial periods](#partial-periods). For the [on-demand quantity strategy](/docs/20260301/product-modules/products/glossary#on-demand-quantity-strategy), see [On-demand quantities](#on-demand-quantities-on-period-of-time-products). ## Partial periods A billing period is partial when the line item covers only some of its days. For example, a line item that starts on February 15, 2024, with monthly billing periods that start on the 1st of each month, covers 15 of the 29 days of February. The [anchor date](/docs/20260301/product-modules/contracts/glossary#anchor-date) of the line item decides the day on which billing periods start. A billing period also splits into parts when the quantity changes partway through it. For example, 10 seats from March 1 to March 15 and 25 seats from March 16 to March 31. For a period-of-time product with the recurring quantity strategy, the [partial-period handling](/docs/20260301/product-modules/products/glossary#partial-period-handling) of the line item decides the amount of each partial part: | Partial-period handling | Amount of a partial part | | - | - | | **Prorate** (default) | The amount of a full billing period, multiplied by the days that the part covers and divided by the days of the full billing period. | | **Charge Full** | The amount of a full billing period. | A pricing preset at \$29 per seat per month, with 10 seats, monthly billing periods that start on the 1st, and a line item that starts on February 15, 2024, gives the following amounts for February: | Partial-period handling | Calculation | Amount | | - | - | - | | **Prorate** | 10 × \$29 × 15/29 | \$150.00 | | **Charge Full** | 10 × \$29 | \$290.00 | A pricing preset at \$30 per seat per month, with 10 seats from March 1 to March 15, 2024, and 25 seats from March 16 to March 31, gives the following amounts for March: | Partial-period handling | Calculation | Amount | | - | - | - | | **Prorate** | 10 × \$30 × 15/31 + 25 × \$30 × 16/31 | \$532.26 | | **Charge Full** | 10 × \$30 + 25 × \$30 | \$1,050.00 | With **Charge Full**, each part of the billing period costs the amount of a full billing period. A quantity change partway through a billing period therefore charges that billing period more than once. For a point-in-time product, the pricing model does not prorate. Each unit costs the full price per unit. The line item can prorate a recurring fixed quantity before the pricing model calculates. See [Line item: quantity](/docs/20260301/product-modules/contracts/concepts/line-items/quantity). The on-demand quantity strategy never prorates. See [On-demand quantities](#on-demand-quantities-on-period-of-time-products). ## On-demand quantities on period-of-time products With the [on-demand quantity strategy](/docs/20260301/product-modules/products/glossary#on-demand-quantity-strategy), a quantity is a purchase at one point in time, not a level that holds over the billing periods. For a period-of-time product, Zenskar charges each unit of an on-demand quantity the full price per unit, in the billing period of the purchase: ```text theme={null} amount = quantity × price per unit ``` The period ratio and the partial-period handling do not apply. The amount is not spread over later billing periods. A pricing preset at \$30 per seat per year, with monthly billing, gives the following amounts: | Quantity strategy | Quantity | Amount | | - | - | - | | Recurring | 100 seats | \$250.00 in each month (100 × \$30 × 1/12) | | On demand | 50 seats bought in August | \$1,500.00 in August, and nothing in the other months | ## Per-unit pricing model on a line item A line item calculates its charges with the per-unit pricing model of its pricing preset. A [price override](/docs/20260301/product-modules/contracts/glossary#price-override) on the line item can change the price per unit and, for a period-of-time product, the pricing period. The pricing model stays per unit. The calculations on this page then use the overridden values. See [Line item: pricing](/docs/20260301/product-modules/contracts/concepts/line-items/pricing). This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.