About Rent Calc

Rent Calc is a scenario calculator for assessing a flat to let and comparing capital decisions.

For each scenario, you can set the initial spend, the expected rent, recurring costs, taxes, vacancy, rental growth, and the alternative use of spare cash.

The result shows not only monthly rent, but final capital over the selected horizon.

• compare renting the flat as is, a light cosmetic refresh, furniture, appliances, and a stronger refurbishment;
• understand whether a higher rent justifies the additional spend;
• consider intermediate options instead of only choosing between refurbishment and savings;
• compare renting with the sale alternative, where the full capital works in savings;
• see the effect of compound return when spare cash flow is moved into savings;
• compare scenarios across short and long horizons.

Rent Calc is not only for the question “should I refurbish or not”.

It can be used when you receive keys to a new build, prepare a flat after tenants move out, assess a resale purchase, consider a light cosmetic refresh, or compare renting with selling.

In each situation, the user builds several scenarios and compares them in one model.

For example: rent as is, do a light cosmetic refresh, add furniture and appliances, fully prepare the flat for rent, do a stronger refurbishment, or compare with the full-capital savings benchmark.

• refurbishment, light cosmetic refresh, furniture, appliances, and property preparation costs;
• the expected rent after the change;
• taxes and recurring operating costs;
• utilities, commissions, and property management fees;
• a reserve for future repairs and upkeep;
• rental growth and property value growth over time;
• the placement of spare cash flow into savings with compound return.

The user defines the property, spare capital, savings rate, and calculation horizon.

Then they configure several preparation and rental scenarios.

After the calculation, the scenarios are compared against each other, the base case, and the savings benchmark.

The calculator does not model a property sale directly. It can only provide an approximate comparison: the savings benchmark shows how the full starting capital could grow if the flat were treated as sold at its current value and all the capital were held in savings.

How that approximation works and what it leaves out is covered in the methodology: How the savings benchmark provides an approximate comparison between letting and selling.

Read more: is it better to let a flat or sell it and put the money in savings?

• the scenario's final capital over the chosen horizon;
• net cash flow after taxes, vacancy, and recurring costs;
• the payback period for the additional spend;
• the difference versus the base scenario and versus the savings benchmark.

How each metric is calculated is covered in the methodology: Which metrics are calculated and what they mean.

On the results page, the comparison table and charts show final capital, net cash flow after vacancy, costs, and taxes, the difference from the savings benchmark, and how long the additional investment takes to pay back.

The methodology explains how to read these visualisations and what the axes represent: How to read the charts.

The user does not get a vague answer like “worth it” or “not worth it”. Instead, they get a comparison of several scenarios in one model.

That makes the decision more concrete: not a feeling about refurbishment or rent, but a discussion based on assumptions, metrics, and planning horizon.

Rent Calc is designed so the calculation can act as structured context for AI analysis.

There is no built-in AI chat in the current version.

• user registration and personal accounts are not available yet;
• the current version uses a fixed set of five scenarios;
• one of these is the base case, with no additional investment, and is used as the comparison point;
• there is no built-in AI chat for analysing results yet.

The methodology explains which factors the model does and does not account for: Limitations of the model and of the current version.

Rent Calc was created by STIV Labs as an applied tool for scenario modelling and decision support.

STIV Labs is the author and developer of the product.