Backsolve Method: A Complete Guide for Founders

Most founders create their plans the same way: start with today’s numbers, add growth assumptions, and see where they land. It seems logical. But this method has a key flaw: your assumptions set your ceiling.

If you assume 20% monthly growth because it feels doable, your plan will show 20% growth. What it doesn’t show is whether 20% is actually enough to hit your next valuation goal, satisfy investor expectations at Series A, or reach profitability before your runway runs out. The Backsolve Model flips this approach completely. Instead of beginning with inputs and seeing what results they produce, you start with the outcome you need and work backward to find what must be true to get there. 

The question shifts from “where will we end up?” to “what does it take to get where we need to be?” This difference matters more than most founders realize. A forward plan showing $2M ARR in 12 months seems like progress until you learn that your Series A investors expect $4M. Backsolve provides that reality check upfront, before you’ve spent six months. executing the wrong plan.

Key Takeaways

• Backsolve planning begins with your target outcome and works backward to identify what needs to happen to achieve it.
• It helps you evaluate whether your goals are realistic given current resources, timelines, and constraints.
• This method is especially useful for setting valuation targets, fundraising schedules, pricing strategies, and growth milestones.
• By prioritizing the desired result over the process, backsolving prevents overly optimistic projections and keeps plans grounded in reality.

What Is the Backsolve Model?

The Backsolve Model is a valuation approach that reverses traditional planning. Instead of projecting forward from today’s numbers, you start with your end goal and work backward to determine what needs to happen to achieve it. 

Traditional planning asks: “If we grow at 15% per month, where will we be in a year?” Backsolve asks: “If we need to reach $5M revenue in a year, what growth rate is required?”The difference is significant because most founders set goals without verifying if their current plan will actually get them there. 

Backsolve Formula

Formula Breakdown

• d1 = [ln(S/X) + (r + σ²/2) × T] / (σ × √T)
• d2 = d1 – σ × √T
• C = Call option value (equity value)
• S = Current equity value
• X = Strike price (breakpoint/liquidation preference)
• r = Risk-free rate
• T = Time to exit (years)
• σ = Volatility
• N(d) = Cumulative standard normal distribution

Given: Recent funding round price per share = P

Solve for: Total equity value (S) such that:

Preferred Share Value = (Total Equity Value × Allocation %) / Number of Shares = P

Then allocate S across all equity classes using option pricing.

When Can You Use Backsolve?

Backsolve isn’t a method that every startup can use at any time. It requires one key condition: a recent, verifiable transaction from an independent investor. That transaction must be either a priced equity round or a convertible note that serves as the basis for the calculation. Without it, there’s nothing to work backward from.

You qualify if:

• You closed a funding round or convertible note within the past 12 months.
• The investor was a third-party and not a founder or related party.

You do not qualify if:

• You have not raised external capital yet.
• Your last round was over 12 months ago.

Applications of the Backsolve Model

The Forward Model and Backsolve Model are two approaches used in the Option Pricing Model (OPM) valuations for private companies, especially startups with complex equity structures. Forward models estimate total equity value directly before allocating it across securities, while backsolve works in reverse from a known transaction price.

Backsolve vs. Forward Modeling

Use Backsolve When	Use Forward Modeling When
You have a fixed target to hit	You're exploring what's possible
Pricing employee stock options	Building internal forecasts
Planning your next fundraising round	Comparing multiple growth strategies
Negotiating investor deal terms	No specific deadline or goal yet

Forward Model

The Forward Model begins with what you have today. You define your current metrics, apply growth assumptions, and calculate where the business will be at a future point in time.

Example:

• Current ARR: $400K
• Assumed growth: 12% per month
• Result after 12 months: $1.55M ARR

This shows the result based on your assumptions, but it doesn’t indicate if that result is sufficient.

Backsolve Model

 The Backsolve Model reverses the process entirely. You begin by defining the outcome you need to achieve by a valuation target, a revenue milestone, or a funding threshold, and work backward to determine what the business must deliver to reach it.

Example:

• Target ARR in 12 months: $2.5M
• Current ARR: $400K
• Required monthly growth: 18%

Why the Backsolve Model Matters for Founders

Backsolve isn’t just a valuation technique. It transforms how you approach planning and decision-making. Here’s why it matters.

• Test Plan Feasibility: Founders often chase ambitious goals without validation. Backsolve reveals whether you’re on track, for instance, if a $40M Series A needs to triple revenue in 9 months but you’re only growing 10% monthly, adjust now instead of failing during fundraising.
• Improves Deal Negotiation: Compare terms like a $30M valuation with 1.5x preference vs. a $25M valuation with 1x. Backsolve quantifies impacts across exit scenarios ($50M vs. $100M), helping you avoid deals that look good but erode equity value.
• Delivers Defensible Common Stock Value: For employee options, IRS rules demand fair market pricing to avoid tax penalties. Backsolve anchors the common stock value to the latest investor transaction, factoring in cap table and preferences, and auditors accept it as market-based.
• Forces Early Reality Check: Comfortable assumptions hide gaps. If your target demands 25% monthly growth but you’ve maxed at 12%, backsolve pushes you to pivot strategy or goals now, saving months of wasted effort.

How the Backsolve Model Works (Real case studies)

We added 2 case studies based on actual company valuations. All identifying details have been anonymized to maintain confidentiality, while preserving the original numbers, structures, and calculations. These examples show the practical application of the backsolve method and provide founders with a step-by-step understanding of the process.

Backsolve Case Study 1: Technology Startup Company Series C Valuation

A precision agriculture technology company raised Series C funding at 45-74 CHF per share in November 2024. The company needed to determine the fair market value of common stock for employee stock option grants. 

Challenges

Using the Series C price of 45.74 CHF directly as the common stock strike price would have overpriced employee options by 77%, creating phantom income tax liabilities for employees and IRC Section 409A compliance risk for the company.

Valuation Summary

Equity Class	Price Per Share (CHF)	Number of Shares	Total Value (CHF)
Series C Preferred	45.74	702,121	32,149,505
Series B Preferred	31.50 - 35.00	1,711,653	40,665,433
Series A Preferred	24.54	430,784	7,077,159
Series Seed Preferred	18.79 - 24.76	147,172	2,292,293
Common Stock	13.41 (before discounts)	105,000	1,407,806
Common Stock - Non-voting	13.41 (before discounts)	602,557	8,078,887
Stock Options	Various	201,209	1,610,927
Total Company Value	-	3,855,496	93,282,010

Observation

The Backsolve analysis identified a 77% difference between the Series C preferred price (45.74 CHF) and the fair market value of common stock (10.66 CHF). Common shareholders receive no proceeds in any exit below 114.4M CHF, the point where all preferred liquidation preferences are fully paid. 

At the current valuation of 93.3M CHF, the common stock is valued only based on future growth potential. Two discounts were applied: 20.5% for lack of marketability and 3% for lack of voting rights on non-voting shares.

Backsolve Calculation – Common Stock

Step	Description	Value (CHF)
Total Equity Value (from Backsolve)	Calculated using the Series C price of 45.74	93,282,010
Value Allocated to Common Stock	Based on the Option Pricing Model	1,407,806
Common Stock Price (before discounts)	Per share value	13.41
Less: Discount for Lack of Marketability (20.5%)	Private company shares cannot be easily sold	-2.75
Less: Discount for Lack of Voting Rights (3.0%)	Non-voting shares only	-0.32
Final Common Stock Value	Fair market value per share	10.66
Final Non-voting Common Stock Value	With both discounts applied	10.34

Preferred vs Common Stock Comparison

Feature	Series C Preferred	Common Stock
Price per share	45.74 CHF	10.66 CHF
Difference	-	77% lower
Liquidation preference	1x (gets money back first)	None (paid last)
Voting rights	Yes	Voting: Yes / Non-voting: No
Downside protection	Strong (preference protects capital)	Weak (loses everything if exit below 114.4M)
Marketability	Can negotiate transfer rights	Cannot sell easily

Series C preferred shareholders paid 45.74 CHF per share, while common stock was valued at just 10.66 CHF, a 77% difference driven entirely by liquidation preferences and marketability discounts.

Outcomes 

• Common stock valued at 10.66 CHF per share (voting) and 10.34 CHF per share (non-voting)
• Both values are set as official strike prices for employee stock options
• Employees are protected from phantom income tax on 34.08 CHF per share that never existed
• Defensible 409A report accepted by auditors and tax authorities
• Company cleared to grant options confidently with full IRC Section 409A compliance

Key Insight

Preferred share prices can be 3-5x higher than the common stock value in the same company. Backsolve reveals this gap before it becomes a problem.

Backsolve Case Study 2: Healthcare Startup B – Convertible Note Round Valuation

A launch-stage medical device startup developing innovative infant feeding products closed a Convertible Notes round (12M Cap) at $1.70 per share in late 2024. The company needed to determine the fair market value of common stock for employee stock option grants under IRC Section 409A.

Challenge

Using the Convertible Notes price of $1.70 directly as the common stock strike price would have overpriced employee options by 56%, exposing employees to phantom income tax liabilities and placing the company at risk of IRC Section 409A non-compliance.

Equity Class	Price Per Share ($)	Number of Shares	Total Value ($)
Common Stock	1.22 (before discounts)	4,310,977	5,239,260
Preferred Stock @ 1.0344	1.47 (before discounts)	681,855	1,004,948
Preferred Stock @ 1.1493	1.51 (before discounts)	147,816	223,132
Preferred Stock @ 1.2642	1.55 (before discounts)	175,760	271,834
Preferred Stock @ 1.7239	1.71 (before discounts)	1,008,259	1,721,944
Preferred Stock @ 2.2986	1.94 (before discounts)	203,963	395,095
Preferred Stock @ 3.6777	2.58 (before discounts)	473,221	1,218,645
Convertible Notes (6M Cap)	1.42 (before discounts)	889,995	1,263,150
Convertible Notes (12M Cap)	1.70 (before discounts)	1,367,082	2,321,860
Warrants @ 0.51	1.03 (before discounts)	2,929	3,011
Warrants @ 1.0124	0.87 (before discounts)	22,622	19,711
Warrants @ 1.44	0.76 (before discounts)	38,048	28,857
Total Company Value		9,322,527	13,711,447

Observation

The Backsolve analysis identified a 56% gap between the Convertible Notes (12M Cap) price ($1.70) and the common stock fair market value ($0.74 after DLOM). Common shareholders receive zero proceeds in any exit below $8,122,369, the point at which all preferred liquidation preferences are fully satisfied. 

The Option Pricing Model (OPM) was applied across 13 breakpoints using a 5-year exit horizon, a 4.33% risk-free rate, and 54.82% volatility. A 39% DLOM was applied to all equity classes, supported by Restricted Stock Studies, the Valuation Advisors Pre-IPO Study, and a Black-Scholes put option model.

Backsolve Calculation – Common Stock

Step	Description	Value ($)
Total Equity Value (from Backsolve)	Calculated using the Convertible Notes (12M Cap) price of $1.70	$13,711,447
Value Allocated to Common Stock	Based on the Option Pricing Model	$5,239,260
Common Stock Price (before discounts)	Per share value	$1.22
Less: Discount for Lack of Marketability (39%)	Private company shares cannot be easily sold	-$0.47
Final Common Stock Value	Fair market value per share	$0.74

Convertible Notes vs. Common Stock Comparison

Feature	Conv. Notes (12M Cap)	Common Stock
Price per share (before DLOM)	$1.70	$1.22
FMV per share (after DLOM)	$1.04	$0.74
Difference	—	56% lower
Liquidation preference	Yes (paid before common)	None (paid last)
Conversion right	Converts to equity	N/A
Downside protection	Strong (capital protected)	Weak (zero below $8.1M exit)
Marketability	Negotiable in the private market	Cannot sell easily

The chart below shows the fair market value per share across all equity classes after applying the 39% DLOM. While the latest Convertible Notes (12M Cap) converted at $1.70, common stock settled at $0.74 – 56% lower, reflecting its last-in-line position in the liquidation waterfall.

Outcomes

•  Common stock valued at $0.74 per share is set as the official strike price for all employee stock options.
•  Preferred stock FMV ranged from $0.90 to $1.57 across all six classes
•  Convertible Notes (12M Cap) settled at $1.04 per share after DLOM
•  Employees are protected from phantom income tax on $0.96 per share that never existed
•  Defensible 409A report accepted by auditors and tax authorities
•  Company cleared to grant options with full IRC Section 409A compliance

Key Insight

When a company has multiple preferred stock classes, convertible notes, and warrants all ahead of common stock, the latest round price can be 50% or more above the actual value of common stock, and Backsolve is the only method that uncovers this gap before it leads to a costly tax issue for employees.

The Gap Is Real – And Backsolve Is How You Find It

Most founders plan by projecting forward from today and hoping the numbers align with their goals. Backsolve does the opposite; it starts with the goal and tells you exactly what needs to be true to reach it. As both case studies demonstrated, the gap between the price of a funding round and the actual common stock value can be 50-77%. Getting that number wrong doesn’t just impact your cap table; it can lead to serious tax issues for your employees. 

If your company has recently closed a round or issued convertible notes, run a Backsolve-based 409A before granting your next options. It’s the most credible, IRS-accepted method available, and it protects everyone involved. Eqvista helps founders get 409A valuations done correctly, quickly, defensibly, and audit-ready.