Free-to-Paid Target for $15k MRR: A Solo Founder Plan

Solving backwards from a revenue target is the right way to design a quarterly growth plan. The math forces specificity: you cannot say "I will do better marketing." You have to say "I will move ARPU from $24 to $30 and trial conversion from 15% to 17%." Then you can decide which of those is plausible. This article walks the calculator on a concrete $15k MRR goal and names the input that actually moves the needle.

1. What the calculator returns for $15k MRR

Inputs: $15,000 target monthly revenue, $420 LTV per paid user, $12 acquisition cost per trial signup, 600 trial signups per month, 6% monthly churn after conversion, $24 ARPU. The engine solves for the steady state: 625 paying customers hold $15k MRR, 6% churn removes 37.5 of them a month, so 37.5 of the 600 monthly signups must convert, a 6.25% trial-to-paid rate. At that rate each paying customer costs $12 ÷ 0.0625 = $192 to acquire, which $24 a month repays in 8 months, and LTV/CAC is $420 ÷ $192 = 2.2.

The 6.25% figure is the conversion rate at which the paid base settles exactly at $15k MRR. It is a steady state, and a steady state takes time to reach: starting from zero at exactly 6.25%, MRR gets to 90% of the target only after about 37 months. Converting at a more typical 15% (90 paid customers a month) puts the eventual base at 1,500 customers, $36k MRR, and crosses $15k in roughly 9 months.

So the question for this plan is not "can I convert enough trials" but "how fast does the base build, and is each customer profitable to acquire." 625 paying customers at 6% monthly churn means 37.5 customers walk out every month; every month of the plan starts by replacing them.

2. ARPU is the lever you control quarterly

Raise ARPU from $24 to $36 (a 50% lift, which a pricing page redesign and a usage-based add-on can plausibly deliver) and the required paid base drops from 625 to 417. At the same 600 signups and 6% churn, only 25 new paid customers a month are needed and the required conversion rate drops from 6.25% to 4.17%. Raise ARPU to $48 (a doubling): required paid base is 313, 18.75 conversions a month, 3.13%. At your actual conversion rate, higher ARPU also shortens payback, because each paying customer repays the same acquisition cost faster.

The point is not that ARPU alone solves the plan. The point is that ARPU is the input that moves the math the fastest, and it is the input the founder can change in 30 days by editing a Stripe price object. Compare to "double trial signups to 1,200": that is a quarter of content, paid ads, or partnership work, with uncertain outcomes.

Paddle's 2024 pricing-and-packaging benchmarks^[2] show median ARPU for solo SaaS in the $25 to $80 range depending on category, with B2B AI-tooling products clustering at the higher end. A $24 ARPU is on the low side for any product with meaningful integration. The right first move on this plan is a pricing experiment, not a marketing campaign. The five numbers before pricing SaaS article covers the diagnostic.

3. Churn after trial eats most of the funnel math

Drop monthly post-trial churn from 6% to 3% (a meaningful but achievable improvement, which a one-quarter retention sprint can deliver). The required paid base for $15k MRR at $24 ARPU stays at 625, but the net-new acquisition required to hold it drops from 37.5/month to 18.75/month, halving the funnel pressure: the required conversion rate falls from 6.25% to 3.13% at 600 signups.

ChartMogul's 2024 SaaS retention report^[4] shows post-trial churn medians of 4% to 8% monthly across self-serve SaaS, with the best decile under 2%. The 6% input in the worked scenario is near the median. There is real room to move this number: at a fixed 15% conversion (90 new paid customers a month), each point of churn changes the eventual steady-state base a lot, from 1,500 customers at 6% to 1,800 at 5% ($7,200 more MRR).

The mechanics of cutting post-trial churn are concrete: onboarding-quality gates (users who complete a specific action in week one churn at half the rate), pricing-tier nudges (annual plans churn 40% to 60% lower than monthly), and exit-survey-driven feature work. The churn reduction guide covers the playbook. None of these are short cycles; budget a quarter for meaningful churn movement.

4. Why trial conversion is not the right obsession

The most common founder reflex when a plan looks slow is "I need to optimize the trial onboarding." This is rarely the right move. As an illustrative ceiling, trial-to-paid conversion tops out around 25% for opt-in flows and 60% for opt-out (credit-card-required) flows^[1]. The plausible improvement window from a typical 15% baseline is 18% to 22%, not 50%+.

The math: a 15% to 22% conversion lift on 600 signups adds 42 paid customers per month. At $24 ARPU, that is $1,008 of new MRR per month of signups, or about 7% of the $15k goal each month. Real, but not transformative. Compare to a $24-to-$36 ARPU lift, which on the same 90 new paid customers a month (600 × 15%) adds $1,080 per month of signups, and also reprices the existing base.

The spread between median and 90th-percentile ARPU is roughly 4x. ARPU has more room to move at the top end, and the top-end gain is more durable because it compounds against the entire paid base rather than just new trials.

5. Picking the one input you can actually move

The discipline: pick the one input you can move this quarter. Two is too many; the experiments interfere. Decision matrix:

• ARPU lift: 30-day experiment, requires a pricing change. Highest leverage. Default first move.
• Post-trial churn reduction: 90-day project, requires onboarding and retention work. Second-highest leverage.
• Trial conversion improvement: 30 to 60 days, requires funnel-flow work. Smallest leverage at this stage.
• Signup volume increase: 90+ days, requires content, paid ads, or partnership work. Highest variance, hardest to predict.

For a founder running this plan from $5k MRR toward $15k MRR, the right sequence is ARPU first, then churn, then conversion, then signup volume. This is the inverse of the order most founders attempt, which is why most plans miss. The revenue forecasting guide covers how to convert these experiment plans into a defensible projection.

6. Sensitivity: ±10% on each input

The calculator returns sensitivity numbers for the conversion rate output. At the worked inputs, a 10% increase in signups (660 instead of 600) drops the required conversion rate from 6.25% to 5.68%. A 10% decrease in signups (540) pushes it to 6.94%. The plan is essentially linear in signup volume around this operating point.

Less obvious: a 10% lift in ARPU (from $24 to $26.40) drops the required paid base from 625 to 568, which at 600 signups maps to a required conversion of 5.68% (the same as a 10% signup increase). ARPU and signup volume are interchangeable on this output, but ARPU is cheaper and faster to change.

A 10% drop in monthly churn (from 6% to 5.4%) does not change the required paid base, but it changes the net new acquisition needed per month from 37.5 to 33.75 (5.63% of signups), a 10% reduction in funnel pressure. Churn improvements are durable because they reduce the maintenance load on the funnel forever, not just for the month they happen.

7. The LTV/CAC sanity check on the plan

The calculator returns an LTV/CAC ratio of 2.2 on these inputs. The $12 is a cost per trial signup; at the 6.25% conversion that holds the target, one paying customer costs $192, and $420 of LTV is 2.2 times that. That is below the 3:1 rule of thumb, and the $12 still excludes founder time, usually the largest input. The true CAC including founder time article works through the loaded-CAC formula.

Plug in a more honest $50 per signup (founder time, content cost, tooling, and a small ad budget for a $24 ARPU product) and, at 6.25% conversion, each paying customer costs $800: LTV/CAC falls to 0.5 and acquisition loses money. Converting at 15% brings that to $333 per customer and 1.3:1. The plan is workable on volume, but only profitable with higher ARPU, lower churn (both raise LTV), or cheaper signups.

The methodology behind the engine's outputs is documented at the Free-Trial-to-Paid Target methodology page^[3], including the derivation of payback months from the cost per paying customer and ARPU. The B2B AI trial conversion benchmarks article covers conversion rate ranges by product category.

Frequently asked questions

How many free trial signups do I need for $15k MRR at $24 ARPU?

At $24 ARPU and 6% monthly churn after conversion, holding $15k MRR takes 625 paying customers, and churn removes 37.5 of them a month. Replacing those takes 37.5 new paid customers a month: about 250 trial signups at a 15% conversion rate, or 208 at 18%.

What is a realistic trial-to-paid conversion rate for solo SaaS?

As an illustrative range, opt-in free trials convert around 14% to 18% and opt-out (credit-card-required) trials around 25% to 60%. At 600 signups a month this plan only needs 6.25% to hold $15k MRR, so conversion is not the constraint; time is, because a paid base builds up over months.

Should I focus on raising ARPU or improving trial conversion?

ARPU. A 25% ARPU lift compounds against the whole paid base every month thereafter; a 25% conversion-rate lift only affects new trials, and the gain is bounded by signup volume. ARPU is the highest-leverage input on the plan for almost every solo SaaS under $50k MRR.

What does the LTV/CAC ratio say about the plan?

At the 6.25% conversion that exactly holds $15k MRR, $12 per signup means $192 per paying customer, so $420 of LTV is 2.2 times CAC: below the 3:1 rule of thumb even before founder time. Converting better than 6.25% lowers the cost per paying customer; a founder-time-loaded $50 per signup at 15% conversion is $333 per customer, about 1.3:1.