Comparison

Rainfall Calculator vs ZappID

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Rainfall Calculator

Calculate potential rainwater harvest volume and cost savings. This tool helps determine annual water collection capacity based on rainfall and roof area, recommending optimal tank sizes for efficient water storage. It also allows for cost-saving analysis by comparing harvested water to mains water prices.

Highlights
  • Instant rainwater calculation
  • Cost savings evaluation
  • Minimum tank size recommendation
  • Supports various input units
  • Formula references included
  • Results copyable to other apps
Features
Read full description

The Rainfall Calculator is a physics/math tool designed to help you determine how many liters/gallons of rainwater you can harvest per year, evaluate cost savings, and recommend the minimum tank size for water storage. Features: - Instant calculation. - Results can be copied to other apps. - Includes formula references. - Supports up to 16 decimal places. - Supports various units for each input. - Works seamlessly on both iPhone and iPad. - Lightweight, compact app optimized for everyday use. - Ad-free and built with privacy in mind. Rainwater Collection Calculator: - The catchment area is multiplied by the depth of rain that falls on it to give the total volume of water produced. - 1 millimeter of rain over 1 square meter of roof equals 1 liter of water. - Annual rainfall (in millimeters) x Roof surface area (in square meters) = Roof catchment capacity. - You can add the cost of mains or tap water per m³ to evaluate the annual cost savings if this rainwater is collected and used instead of drinking water. - The minimum tank size should store 33% of the "Annual Rainfall On Your Roof Area" as you will use the water while you are collecting it. The rain will collect in gutters that channel the water into downspouts and then into some sort of storage vessel. Rainwater collection systems can be as simple as collecting rain in a rain barrel or as elaborate as harvesting rainwater into large cisterns to supply your entire household demand. You can also collect rainwater for garden use. Plants prefer rainwater because it's naturally soft and free of chlorine and other chemicals. If drought is a problem where you live, collecting rainwater is a good way to handle watering restrictions. If you're on a municipal water system, you can save a considerable amount of money. Thank you for your support! Visit nitrio.com for more apps for your iOS devices.

About

ZappID

Features
Read full description

Create your ZappID and send push notfictions fast and very easy by accessing a url or send a api-request.

Screenshots

Rainfall Calculator4 screens
ZappID3 screens

Verdict

The call

The clearest difference is price: ZappID at Free against Rainfall Calculator's $2.99. ZappID also leads on update cadence (every 4 days vs every 29 months). Rainfall Calculator's advantage is chart position (#176 vs unranked). On ads, in-app purchases, device support and iOS requirement there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

ZappID is free to download; Rainfall Calculator costs $2.99 up front. Neither carries in-app purchases, so what you see is what you pay.

UpkeepUpdate frequency

Rainfall Calculator ships an update every 29 months, ZappID every 4 days. The most recent releases landed on September 9, 2026 and September 15, 2026 respectively.

Scorecard3 real differences · 7 level
Rainfall Calculator versus ZappID: the parameters behind the verdict, then further details
ParameterRainfall CalculatorZappID
Price$2.99Free — better
Rating5.0 (1 ratings) — better—
Number of ratings1 — better—
Update frequencyEvery 29 monthsEvery 4 days — better
AdsNoNo
In-app purchasesNoNo
MonetizationPaid—
Best chart rank#176 — better—
DevicesiPhone, iPad, iPod — betteriPhone, iPod
Requires iOS1312.0 — better
Further details — not scored
Size1 MB11 MB
Age rating4+4+
DeveloperNitrioFredrik Petersson

In-app purchases

None

Rainfall Calculator

No in-app purchases

None

ZappID

No in-app purchases

Questions

Is Rainfall Calculator free?
Rainfall Calculator costs $2.99, with no in-app purchases.
Is ZappID free?
ZappID is free to download, with no in-app purchases.
Do Rainfall Calculator or ZappID have ads?
Neither Rainfall Calculator nor ZappID shows ads.
Which is updated more often, Rainfall Calculator or ZappID?
Rainfall Calculator ships an update every 29 months, and ZappID every 4 days. Most recently, Rainfall Calculator was updated on September 9, 2026 and ZappID on September 15, 2026.

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