Comparison

Hydrology Formulator vs Compare Flow

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

Head to head
About

Hydrology Formulator

This app provides a comprehensive collection of over 1,000 formulas, calculators, and conversions for hydrology and civil engineering. It covers a wide range of topics including groundwater, stormwater, pipe flow, and water pollution.

Highlights
  • 1,000+ formulas and calculators
  • Groundwater analysis tools
  • Stormwater design calculations
  • Open channel and pipe flow equations
  • Water pollution modeling
  • Conversions and reference data
Features
Read full description

HYDROLOGY FORMULATOR is the ultimate pocket reference for hydrologists, civil engineers, environmental scientists, and students. Packed with 1,000+ formulas, calculators, and conversions, it covers everything from groundwater analysis to stormwater design — all in one powerful app. HYDROLOGY CALCULATORS Infiltration & Recharge — 17 Calculators - Porosity, Green-Ampt Infiltration, Horton Infiltration, Philip Infiltration, Holtan's Model, Hydraulic Conductivity, Groundwater Recharge, Mean Pore Velocity, Specific Discharge, Volumetric Water Content, and more Evaporation & Transpiration — 8 Calculators - Penman-Monteith ET0, Blaney-Criddle ET, Thornthwaite PET, Crop Evapotranspiration, Saturation Vapor Pressure, Evaporation Rate of Lake, Relative Humidity, Potential Evapotranspiration Open Channel Flow — 12 Calculators - Manning's Equation (SI & US), Chezy Equation, Froude Number, Hydraulic Radius, Hydraulic Jump, Critical Depth, Specific Energy, Reynolds Number, and more Pipe Flow — 7 Calculators - Darcy-Weisbach Equation, Hazen-Williams Velocity (SI & US), Reynolds Number, Water Hammer Pressure, Continuity Equation, Minor Head Loss Stormwater & Watershed — 9 Calculators - SCS Curve Number Runoff, SCS Peak Discharge, IDF Rainfall Intensity, Kirpich Time of Concentration, Gumbel Extreme Value, Detention Storage Volume, Composite Curve Number, and more Pumps & Water Supply — 7 Calculators - Total Dynamic Head, Water Horsepower, Brake Horsepower, NPSHa, Affinity Laws for Flow, Head, and Power Weirs & Orifices — 6 Calculators - Rectangular Weir (SI & US), V-Notch Weir, Broad-Crested Weir, Orifice Flow, Spillway Discharge Water Flow — 10 Calculators - Water Flow Rate, Velocity of Water, Volume of Water Flow, 90° V-Notch calculations, Pipe Total Diameter, and more Surface Runoff — 6 Calculators - Average Velocity, Runoff, Travel Time, Hourly Rate of Rainfall Groundwater — 7 Calculators - Darcy's Law, Thiem Equation, Cooper-Jacob Drawdown, Dupuit Well Flow, Radius of Influence, Storage Properties Soil Pollution — 5 Calculators - Groundwater Pore Velocity, Effective Diffusion, Hydrodynamic Dispersion, Aquifer Parameter, Variance of Pore Velocity River Pollution — 7 Calculators - River Oxygen Deficit, Critical Time & Distance for Oxygen Deficit, Re-Aeration Constants, Dissolved Oxygen, River Flow, Water Temperature Lake Pollution — 4 Calculators - Waste Entering, Equilibrium Concentration, Settling Loss Rate, Particle Deposition Rate Sediment Transport — 4 Calculators - Shields Parameter, Bed Shear Stress, Stokes' Law Settling Velocity, Meyer-Peter Müller Bedload Snow Hydrology — 2 Calculators - Snow Water Equivalent, Degree-Day Snowmelt Culvert Hydraulics — 2 Calculators - Culvert Headwater (Outlet Control), Culvert Outlet Control Head Loss Flood Routing - Muskingum Routing Water Balance - Water Balance Equation, Storage Continuity Plus: Area Formulas, Pollution Cleanup, and more CONVERSIONS & REFERENCE Hundreds of built-in conversions across 16 categories including: - Liquid Measures, Cubic Measures, Linear Measures, Square Measures - Flow Rates, Pressures, Horsepower, BTU, Watts, Power - Hydraulic Conversions, Sand-to-Volume, Ft-Lbs - 8 Temperature Scales (Celsius, Fahrenheit, Kelvin, Rankine, Réaumur, Newton, Delisle, Rømer) - Metric Conversions and Fraction Conversions KEY FEATURES - Save and review past calculations - Switch between US (Imperial) and Metric units - Clean, intuitive interface designed for field and office use - Premium upgrade unlocks Groundwater, Pollution, Sediment Transport, Snow Hydrology, Culvert Hydraulics, and Flood Routing calculators

About

Compare Flow

This application helps engineers and designers evaluate the hydraulic flow capacity of various non-pressure sewer pipe types. It allows for comparisons between different pipe geometries and materials, including concrete, thermoplastic, and metal options.

Highlights
  • Manning's Formula calculation
  • Compare hydraulic flow capacity
  • Evaluate pipe geometry alternatives
  • Compare pipe material options
  • Supports concrete, thermoplastic, and metal pipes
  • Circular, elliptical, arch, and box sections
Features
Read full description

Compare Flow app uses Manning's Formula, the most widely accepted formula for evaluating the hydraulic capacity of non-pressure sewers. In order to evaluate possible alternatives in either pipe geometry or material, use this app to compare the hydraulic flow capacity among various concrete pipes including circular, elliptical, arch and box sections with circular thermoplastic and corrugated metal pipes.

Screenshots

Hydrology Formulator4 screens
Compare Flow4 screens

Verdict

The call

The clearest difference is review sentiment: Compare Flow at 50% against Hydrology Formulator's 0%. Compare Flow also leads on in-app purchases (none vs 1) and ratings volume (5 vs 1). Hydrology Formulator's advantage is rating (5.0 vs 4.6) and update cadence (every 6 months vs every 32 months). On price, ads, monetization model and device support 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

Both are free to download. Hydrology Formulator sells 1 one-off in-app purchase. Compare Flow asks for nothing beyond the download.

ReceptionRating · Positive reviews · Number of ratings

Hydrology Formulator holds the better App Store score, 5.0 against 4.6. That said, the two scores are not equally well evidenced: Compare Flow has 5 ratings behind it against 1, so its average is the more settled of the two. Written reviews complicate that: 0% of Hydrology Formulator's written reviews are positive against 50% of Compare Flow's, so the app with the better star average is not the one people write more warmly about.

UpkeepUpdate frequency

Hydrology Formulator ships an update every 6 months, Compare Flow every 32 months. The most recent releases landed on October 8, 2026 and October 4, 2026 respectively.

Scorecard6 real differences · 4 level
Hydrology Formulator versus Compare Flow: the parameters behind the verdict, then further details
ParameterHydrology FormulatorCompare Flow
PriceFreeFree
Rating5.0 (1 ratings) — better4.6 (5 ratings)
Positive reviews0.0% of reviews50.0% of reviews — better
Number of ratings15 — better
Update frequencyEvery 6 months — betterEvery 32 months
AdsNoNo
In-app purchasesYesNo — better
MonetizationFreeFree
DevicesiPhone, iPadiPhone, iPad, iPod — better
Requires iOS18.615.1 — better
Further details — not scored
Size18 MB23 MB
Age rating4+4+
DeveloperHistorycentral.comiENGINEERING Corporation

Customer experience

Hydrology Formulator

All ratings1 ratings
Positive100.0%
Neutral0.0%
Negative0.0%
Written reviews5 reviews
Positive0.0%
Neutral40.0%
Negative60.0%

Compare Flow

All ratings5 ratings
Positive80.0%
Neutral20.0%
Negative0.0%
Written reviews2 reviews
Positive50.0%
Neutral50.0%
Negative0.0%

In-app purchases

1 purchases

Hydrology Formulator

One-time1
  • Pro Version$3.99
None

Compare Flow

No in-app purchases

Questions

Is Hydrology Formulator free?
Hydrology Formulator is free to download, with in-app purchases available.
Is Compare Flow free?
Compare Flow is free to download, with no in-app purchases.
Which has better reviews, Hydrology Formulator or Compare Flow?
Hydrology Formulator is rated higher. Hydrology Formulator averages 5.0 out of 5 from 1 ratings, while Compare Flow averages 4.6 from 5 ratings.
Do Hydrology Formulator or Compare Flow have ads?
Neither Hydrology Formulator nor Compare Flow shows ads.
Which is updated more often, Hydrology Formulator or Compare Flow?
Hydrology Formulator ships an update every 6 months, and Compare Flow every 32 months. Most recently, Hydrology Formulator was updated on October 8, 2026 and Compare Flow on October 4, 2026.

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