Start with what the spreadsheet genuinely wins
Most comparisons like this are written by whoever sells the alternative, which is why they are not worth reading. So, plainly: for a lot of people, a development feasibility spreadsheet is the correct tool and switching would be a downgrade.
A staged land subdivision with a deferred settlement and a profit share on the second stage does not fit a form. In a spreadsheet you build the structure you actually have. In software you model the nearest structure it offers, and hope the difference does not matter.
Everyone already has the tool and already knows how to use it. For an occasional deal, that is a real advantage and it is not a small one.
Every formula is one click away. There is no engine deciding something on your behalf that you cannot inspect, which is a legitimate reason for a careful modeller to prefer one.
If those three describe your situation, stop here. Nothing below is going to change the answer, and a tool you fight is worse than a file you understand.
Where they break, and why it is structural
These are not carelessness. They follow from what a spreadsheet is — a private file with no concept of a record, a version or a source — and no amount of discipline removes them, because the discipline has to be reapplied by every person who touches the file.
Nobody builds a feasibility from a blank sheet. You copy the last one, which was copied from the one before, and inherit assumptions nobody in the room chose — a contingency set for a different site, a rate from a different year, a formula that stopped referring to the cell you think it does.
The moment two people need the same number, the file is emailed, edited, and returned. Now there are two, they disagree, and neither carries a record of which assumption moved.
A rate typed directly into a formula is invisible to everyone but its author, and to its author six months later. The number is auditable; the reasoning behind it is not.
Zone, overlays, lot area and frontage come from a map, get read by a human, and get typed into a cell. That is a transcription step on the inputs the entire answer rests on, repeated for every deal, with nothing checking it.
Ask two people on the same deal for the margin. If the answer arrives as a file rather than a figure, and the two files disagree, the spreadsheet has stopped being a model and become a distribution problem. That is the moment worth acting on, not a birthday or a budget cycle.
Side by side, without pretending
| Dimension | Spreadsheet | Dedicated software | Edge |
|---|---|---|---|
| Unusual deal structures | Build exactly what you have | Model the nearest thing it offers | Spreadsheet |
| Cost for an occasional deal | You already own it | A subscription whether or not you use it | Spreadsheet |
| Site data | Read off a map and retyped | On the record the numbers run against | Software |
| Two people, one number | Two files, both called final | One record, one answer | Software |
| Where an assumption came from | In the author’s head | Stated and dated beside the figure | Software |
| Sensitivity | Rebuild it by hand, per scenario | A property of the model | Software |
| Duty and GST by state | A schedule you maintain yourself | Maintained, and wrong loudly rather than quietly | Software |
| Handing it to a bank | Universally accepted | Export, then universally accepted | Even |
Three of eight go to the spreadsheet or are even. Any comparison that gives you eight out of eight is selling something.
What you give up by switching
The honest cost of moving off a spreadsheet is not the subscription. It is three things nobody mentions.
You inherit someone else’s defaults. A blank cell is obviously blank. A field pre-filled with a plausible contingency, a plausible interest rate and a plausible selling cost is not, and it will be accepted without being chosen. Any tool worth using discloses every default it applied; if you cannot see the list, that is the answer to whether to use it.
You lose some structural freedom. The deal you can model is the deal the tool models. For most residential development that is not a constraint. For the deals that do not fit the tool’s structure it is the whole ballgame.
You have to learn where things are. For a week or two you will be slower. That is a real cost and it is worth naming, because it is the reason most switches fail — not the tool, the fortnight.
Five questions that decide it
| How many people need to read the same number? | One person, one deal, one decision: a spreadsheet is fine. The moment a valuer, a broker and a partner all need the same figure, the file stops being a model and becomes a distribution problem. |
| How often does the site data change under you? | If you screen many sites, you retype zone, area and frontage for each one. That is the step that is both the most mechanical and the most consequential to get wrong. |
| Could you defend every assumption six months from now? | Not "is the number right" — "where did it come from". If the answer lives only in your memory, the study cannot be reviewed by anyone else, including future you. |
| Do you need sensitivity, or one answer? | If you only ever present the base case, a spreadsheet is enough. If you are asked what happens when construction runs ten per cent over, and you have to rebuild the model by hand to say, you will stop being asked. |
| Is your structure genuinely unusual? | If it is, stay in the spreadsheet and do not let anyone talk you out of it. Forcing a structure into a tool that does not model it produces a confident number about a project you are not doing. |
The cheapest test is not a trial, it is a comparison. Take a deal you have already modelled by hand and run it again somewhere else. Either the numbers agree, and you have confirmed your spreadsheet, or they do not, and the disagreement will tell you which assumption one of them is treating differently. Both outcomes are worth an hour.
If you want the underlying method rather than the tooling question, the guide to preparing a feasibility study works through a full Australian example with sensitivity, and the product page sets out what this one does.
Test the difference on a deal you already know
Run a site you have already modelled by hand and compare the two. If the numbers agree, you have learned something about your spreadsheet; if they do not, you have learned something more useful.