Kids STEM Subscription Box Break-Even: ~$35k Monthly Revenue

Fixed costs $3.9K/mo Run-rate base

Contribution margin 80.5% After variable costs

Break-even revenue $4.8K/mo Cover fixed base

Break-even timing Month 28 Full-model break-even

Break-even calculator

Test monthly revenue, direct costs, and overhead to see when the box covers fixed costs.

Lean Base Full

Monthly revenue Revenue sets the margin pool that covers fixed costs. $ Low sales High sales Variable expenses These are direct kit, shipping, and ad costs that move with sales. $ Low cost High cost

Money available to cover fixed costs $52,820 $63,565 revenue - $10,745 variable expenses

Margin ratio

83%

Covers fixed costs

Yes

Fixed monthly costs This is the monthly overhead the business must cover. $ Low overhead High overhead

Break-even chart Revenue Total costs

Which expenses are fixed and which move with sales for a kids STEM subscription box?

Cost classification

Break-even gets reliable only when each expense matches how subscriber volume behaves. Treat materials, shipping, payment fees, and performance marketing as volume-linked, but keep platform tools, rent, and staffing separate.

Expense	Cost	Break-Even Treatment	Common Mistake
Kit Materials & Packaging	Variable	Use 8.0% of revenue in the first year, improving to 6.0% by the fifth year.	Modeling every box at the same gross margin.
Shipping & Fulfillment	Semi-variable	Use 5.0% of revenue in the first year, improving to 4.0% by the fifth year.	Treating shipping as fully fixed despite order volume.
Performance-based Marketing & Advertising	Variable	Use 4.0% of revenue in the first year, falling to 2.5% by the fifth year.	Mixing performance spend with the fixed annual marketing budget.
Payment Processing Fees	Variable	Use 2.5% of revenue in the first year, easing to 2.2% by the fifth year.	Forgetting that card fees rise with paid subscriptions.
E-commerce Platform Fees	Fixed	Use $500 per month from Month 1 through Month 60.	Scaling it with revenue instead of keeping it flat.
Subscription Management Software	Fixed	Use $300 per month from Month 1 through Month 60.	Double-counting it inside platform fees.
Office & Storage Rent	Semi-fixed	Use $1,500 per month until capacity needs force a step up.	Assuming rent moves smoothly with every subscriber.
Staff Wages	Semi-fixed	Model salaries in steps as full-time equivalent staffing rises by year.	Treating all payroll as fixed forever.

How does break-even shift from lean to full for a kids STEM subscription box?

Scenario table

Higher-priced tiers lift revenue per active subscriber, but fixed load rises too, so break-even only improves if volume keeps up. Lean is the tightest case; full has the best margin, but it still needs a larger subscriber base.

Planning cases only; these are model assumptions, not guaranteed results.

Scenario	Monthly Revenue	Variable Costs	Fixed Costs	CM Ratio	Operating Profit	Break-Even Signal
Lean launch mix	$3,288	$641	$19.9k	80.5%	-$17.3k	This is the tightest case, and it still needs about 903 subscribers with Year 1 marketing included.
Base year 3 mix	$3,692	$624	$27.6k	83.1%	-$24.5k	Margin improves, but the higher fixed load still points to about 1,078 subscribers at break-even.
Full year 5 mix	$4,109	$604	$36.6k	85.3%	-$33.1k	Best margin, but the bigger overhead means break-even only moves up to about 1,253 subscribers.

What breaks the break-even plan for this kids STEM subscription box?

Stress test

The plan breaks if signups miss the 1,060 target, if variable expense rises above the Year 1 19.5% level, or if payroll grows before volume does. Those hits can push break-even past Month 28 and above the $394k cash floor.

Stress Case	Changed Assumption	Break-Even Revenue	Revenue Gap	Risk Signal
Current plan	No change in Year 1 pricing, conversion, or overhead.	$349,000	$0 cushion	Month 28 is the first break-even point.
Revenue shortfall	Trial-to-paid conversion slips from 70.0% to 65.0%.	$349,000	$24,900 gap	A small conversion miss cuts headroom fast.
Fixed-cost increase	Customer support moves from 0.5 FTE to 1.0 FTE in Year 1.	$376,800	$27,800 gap	Payroll rises before subscriber density supports it.
Margin pressure	Variable expense rises from 19.5% to 21.5% of revenue.	$357,900	$8,900 gap	Higher kit, shipping, and fee costs squeeze margin.
Combined pressure	Conversion falls to 65.0%, support reaches 1.0 FTE, and variable expense rises to 21.5%.	$386,700	$37,700 gap	The miss stacks up and cash need climbs above the $394k floor.

Is the kids STEM box ready for inventory, hiring, and paid growth?

Founder checklist

Do not commit cash yet unless you can prove 1,060 active subscribers, 70.0% trial-to-paid conversion, and CAC near $60. Here’s the quick math: Year 1 weighted revenue is about $32.88 a month per subscriber, so the funnel has to cover the fixed load before you buy inventory or add hires.

1Paid Base1,060 subs

Verify you can reach 1,060 active subscribers before deep inventory, because that is the break-even demand test and it only works if CAC stays near $60.

2Revenue Mix$32.88/mo

Check the weighted monthly revenue per active subscriber from the Year 1 mix, because the model only works if that average holds.

3Contribution80.5% CM

Keep kit materials and shipping at 13.0% of revenue before ads and fees, or the 80.5% contribution margin will slide.

4Trial Rate70.0%

Prove free-trial-to-paid conversion at 70.0% before you buy traffic, because checkout and billing have to work before scale.

5Staff Ramp3.5 FTE

Hold the launch team at 3.5 FTE until paid demand covers the fixed load, because Year 1 payroll is about $240k a year before the rest of overhead.

6Cash Runway$394k / M28

Stage the $45k core launch build and keep the $394k cash cushion to Month 28, or rent and warehouse setup will outrun the funnel.