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 CAC per signup, 600 trial signups per month, 6% monthly post-trial churn, $24 ARPU. The engine computes that you would need to convert 625 of 600 signups — a required conversion rate above 100% (the raw figure is ~104%). Since you cannot convert more users than sign up, cap the read at 100% and treat it as a hard infeasibility signal: at 600 signups the plan does not exist. To make it feasible at a realistic conversion ceiling, you need roughly 2,500 signups per month (at a best-case ~25% opt-out ceiling) to 3,800 (at a typical 15–18% opt-in rate) — not 600. The other outputs: 625 paid users required at steady state, payback of 0.5 months, and an LTV/CAC ratio of 35.

The 104% conversion rate is the headline output that founders look at first, and it is also a tell. Trial-to-paid conversion above 100% is mathematically impossible (you cannot convert more users than signed up). When the calculator returns this, it is saying the plan does not exist at the current signup volume. Either signups have to triple, ARPU has to climb meaningfully, or churn has to drop, or some mix of all three.

The other outputs are more informative. 625 paid users is the steady-state paid base required to hold $15k MRR at $24 ARPU. With 6% monthly churn, that means 37.5 users churn every month, so net-new paid users from trials must equal 37.5 per month just to hold position, plus the growth quota on top of that.

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, the required conversion rate drops from 104% to roughly 69%. Still infeasible. Raise ARPU to $48 (a doubling): required paid base is 313, conversion needed is roughly 52%. Still high.

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 "increase trial signups from 600 to 3,000" — that is a quarter of content, paid ads, or partnership work, with uncertain outcomes.

Paddle's 2024 pricing-and-packaging benchmarks^[3] 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 same plan now demands 52% conversion at 600 signups, infeasible but materially less so.

ChartMogul's 2024 SaaS retention report^[5] 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, and every percentage point of churn improvement is worth roughly $6,000 of annualized revenue at steady state on this plan.

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 the calculator says "104% conversion needed" 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 users per month. At $24 ARPU, that is $1,008 of monthly revenue lift, or about 7% of the $15k goal. Real, but not transformative. Compare to a $24-to-$36 ARPU lift, which on the same 90 paid users (600 × 15%) adds $1,080 per month immediately, without any funnel-flow work.

The Paddle / ProfitWell free-trial conversion data^[2] reinforces this: the spread between median and 90th-percentile trial-to-paid conversion is roughly 12 points (15% vs 27%). 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 104% to 94.7%. A 10% decrease in signups (540) pushes it to 115.7%. 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 94.7% (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 — 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 35 on these inputs ($420 LTV, $12 CAC). A 35:1 ratio is implausible for any real solo SaaS. The honest reading is that the $12 CAC excludes founder time, which is the largest input. The true CAC including founder time article works through the loaded-CAC formula.

Plug in a more honest CAC of $50 per signup (founder time, content cost, tooling, and a small ad budget for a $24 ARPU product) and the LTV/CAC ratio drops to 8.4:1. Still healthy by SaaS benchmarks (3:1 is the rule of thumb), but no longer suspiciously high. The plan is real, just not as profitable as the headline numbers suggested.

The methodology behind the engine's outputs is documented at the Free-Trial-to-Paid Target methodology page^[4], including the derivation of payback months from CAC and gross margin. 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% post-trial monthly churn, the steady-state paid base required is 625 paying users. The signups required depend on conversion rate; at a realistic 15% to 18% trial-to-paid conversion, that maps to roughly 3,500 to 4,200 trial signups per month.

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%. The 100%+ conversion rate the calculator returns at 600 signups simply means the plan is mathematically infeasible at that signup volume.

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 an LTV/CAC ratio of 35 mean for the plan?

It means CAC is wildly underestimated. A 35:1 ratio is the calculator running against a $12 CAC-per-signup assumption that excludes founder time. Plug in a realistic founder-time-loaded CAC of $40 to $80 per signup and the ratio compresses to a defensible 5:1 to 10:1 range.