The challenge
A UK organization that helps businesses measure sustainable impact wanted its users to see a venture whole: the money it makes, and what it does for the environment and for people. We built and delivered a triple bottom line calculator for it as a six-week web MVP.
The idea is easy to state and harder to model. A business plans an investment, chooses the UN Sustainable Development Goals it targets, and wants to know if the plan holds up on all three counts for five years.
A spreadsheet strains under that. Each lens needs its own inputs, totals must update as numbers change, and every user's figures must stay private. People also had to sign in with the accounts they already hold on the organization's website.
It supplied wireframes. We turned them into calculation logic, a secure back end and an interface that responds as you type.
What we built
The calculator is a React front end on Node.js REST APIs, with MongoDB, server-side PDF generation and hosting in the organization's own AWS account. Everything hangs off a five-year model: Year 1 to Year 5, plus a Summary.
Five-year framework. Each year has its own annual investment and data container, a real-time calculation engine runs underneath, and a reset-all clears the slate.
Financial performance. Several plans per year. Revenue is quantity times unit price, costs are quantity times unit cost, and totals and net profit or loss fill in automatically.
SDG selection and mapping. Users pick several SDGs per year. Those picks switch on the impact modules, show visual indicators and record each year's SDG focus.
Environmental and social impact. Two modules with one pattern: positive and negative outcomes go in, and a net impact with monetized values comes out.
Overall performance dashboard. A live panel with the combined TBL value and its three parts, a positive, neutral or negative status, the Net Present Value of impact and the Return on Sustainable Outcome.
PDF reports. A report for each year from 1 to 5 and a consolidated five-year summary, generated on demand.
Year-wise summaries from each module feed the overall view, so a change in Year 3 moves the five-year picture.
How it works day to day
Picture a founder weighing up a new product line. They sign in with their existing account and land on their own calculator, which nobody else can see.
In Year 1 they enter the investment and a financial plan or two. Next they choose the SDGs the venture targets, which opens the environmental and social modules. There they record the good and the harm they expect, each with a money value.
The dashboard updates as they type. They step through Years 2 to 5, check the Summary, then download a PDF for one year or all five to share with a board or funder.
The result
We delivered the calculator as a six-week MVP in four milestones: requirements, calculation logic and technical design from the client's wireframes; the core back end and live calculator; the five-year dashboard and consolidated PDF; then testing and fine-tuning.
What it makes possible: a business can test an impact plan across three lenses and five years before committing, and leave with a report it can pass on.
The design is GDPR-ready, with minimal personal data and encryption at rest and in transit, and it targets current desktop Chrome, Firefox, Safari and Edge. We don't publish usage figures for this project.
What the research says
Impact data still lives in spreadsheets. In a KPMG survey of 550 board members, executives and managers, 83% said their organization was ahead of peers on sustainability reporting, yet 47% still used spreadsheets to manage their ESG data (KPMG ESG Organization Survey, 2024). A calculator with built-in calculation logic and live totals replaces the hand-built sheet.
Every new password is a new risk. Verizon's 2025 Data Breach Investigations Report found that about 88% of breaches in its basic web application attack pattern involved stolen credentials (Verizon DBIR 2025). Letting people sign in with the accounts they already hold on the organization's website avoids creating one more password to steal or reuse.
Breaches are expensive. IBM's 2026 Cost of a Data Breach report puts the global average cost of a breach at $4.99 million (IBM, vendor research). Keeping personal data to a minimum and encrypting it at rest and in transit limits what any incident could expose.
Where AI fits next
These are possibilities, not features of the MVP. An assistant could suggest SDGs that suit a plan from a short description of the venture. It could also flag inputs that look out of line with earlier years.
Planning a triple bottom line calculator?
Most of the effort sits in the model, not the screens. Settle these before you build:
How will you put a money value on environmental and social outcomes, and who signs those values off?
How many years should the model cover, and what discount rate sits behind any present-value figure?
Will people sign in with accounts they already hold elsewhere, and which system owns that identity?
What does a downloadable report need to show before a board, a funder or an auditor will trust it?
Scoping your first version? Our guide to building a SaaS MVP covers what to cut. You can also see how we run custom software projects and SaaS and MVP builds.
Related builds are collected under software products and SaaS.
