EStore Tools

Open-to-Buy Calculator

Work out how much buying budget you have left for a period, at retail and at cost, before you overbuy against your sales plan.

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Your numbers

Plan for the period
$
$

What you want on hand at the end of the period, at the price you'll sell it for.

$
Where you stand now
$
$
Convert to cost

Used only to convert the retail figure to a cost figure.

%

Your result · updates as you type

Open to buy

$44,000

You can commit to $44,000 more at retail ($22,000 at cost) before the period ends and still land on plan.

OTB at retail
$44,000
OTB at cost
$22,000
Committed now (stock + on order)
$54,000

This is a single-period snapshot. Recalculate it as sales, receipts and markdowns actually happen, since OTB drifts fast in a busy season.

Breakdown

Planned sales
$40,000
Planned markdowns
$3,000
Planned end-of-period stock
$55,000
Stock on hand + on order
−$54,000
Open to buy (retail)
$44,000
At cost (50% margin)
$22,000

The open-to-buy formula

Open to buy (retail) = planned sales + planned markdowns + planned end-of-period stock − (stock on hand + stock on order)

Example: the default numbers

Planned sales + markdowns + planned EOM stock
$40,000 + $3,000 + $55,000 = $98,000
Stock on hand + on order
$48,000 + $6,000 = $54,000

OTB at retail = 98,000 − 54,000 = $44,000. At a 50% margin, that's $22,000 at cost you can still commit before the period ends.

A negative result means you're overbought: what's already on hand or on order exceeds your plan, so buying more will push end-of-period stock over target.

Using OTB day to day

  1. 01

    Plan monthly, check weekly

    Recalculate as sales, receipts and markdowns actually happen. OTB drifts fast in a busy season.

  2. 02

    Buy against it, not against gut feel

    Before placing a new purchase order, check it fits inside the remaining OTB, at cost.

  3. 03

    If overbought

    Cancel or push back part of what's on order before you commit to anything new, rather than letting end-of-period stock run over plan.

Questions people ask

What is open to buy?

The dollar amount of merchandise you can still purchase in a period without exceeding your planned end-of-period stock level.

What does it mean to be overbought?

Your current stock plus what's already on order already exceeds the plan for the period, so any new purchase orders will push you further over target.

Why does the calculator show both retail and cost figures?

Buying plans are usually set at retail value, but purchase orders are placed at cost. The margin field converts between the two.

How often should I recalculate OTB?

Weekly is common in fast-moving retail, since sales, receipts and markdowns all shift the number.

Related tools

Sell-Through Rate CalculatorFind what share of the stock you had available actually sold, in retail mode (units received) or reseller mode (stock on hand plus received).Inventory Turnover CalculatorSee how many times you sold through your average inventory in a period, and how many days stock typically sits before it sells.EOQ CalculatorFind the order quantity that minimizes ordering cost and holding cost combined, using the classic economic order quantity formula.GMROI CalculatorPaste a list of SKUs with gross margin and average inventory cost, and see gross margin return on inventory for each one, ranked.

Want this builtinto your store?

I'm Emmanuel, a Shopify and WooCommerce developer. If this tool pointed at something you'd rather have fixed for you (a faster store, cleaner product data, a migration, a custom feature), send me a note.

Emmanuel Asika

Emmanuel Asika

Shopify & WooCommerce developer, Dublin

I build and fix online stores: new builds, migrations, speed, SEO and the custom bits apps can't do.

hello@emmanuelasika.com
See my work

Last reviewed 30 September 2026.