1
Decision-focused
Each tool starts from a real reef task, from preparing saltwater to checking coral compatibility.
Free reef tools - 12 calculators
Reef tank calculators and coral care tools.
12 free tools for planning a reef tank, preparing saltwater, and making better-informed coral care and placement decisions.
Browse all 12 toolsTool directory
Find the right reef tool.
Start with coral care or jump to the setup calculation you need.
Coral care tools
Check coral requirements, compatibility, spacing, light, flow, and placement before making a change in the reef tank.
Coral care
Coral care requirements lookup
Look up typical care requirements for common soft corals, LPS and SPS.
- Difficulty
- Light & flow
- Warning signs
Coral care
Coral compatibility checker
Check whether coral pairs or a new coral plan are likely compatible in your reef tank.
- Care overlap
- Mixed reef risk
- Tank readiness
Coral care
Coral aggression & spacing checker
Check coral spacing risk from coral type, distance, expansion, flow, growth, stress signs, and shading.
- Sweeper risk
- Overgrowth
- Spacing buffer
Coral care
Coral flow requirements finder
Check coral flow requirements and direct-blast risk from coral type, polyp movement, and detritus signs.
- Flow intensity
- Direct blast
- Turnover hint
Coral care
Coral PAR calculator
Check whether measured or estimated reef tank PAR is likely low, high, or in range.
- Measured PAR
- Estimated PAR
- Light range
Coral care
Coral placement finder
Match a coral's likely light and flow needs to the right zone in your aquascape.
- Light zone
- Flow zone
- Aggression
Reef setup calculators
Plan usable water volume, rock, sand, saltwater mixing, salinity, and water changes.
Aquascape planning
Live rock calculator
Estimate live rock, dry rock, mixed rock, box count and displacement from display volume, aquascape style and rock density.
- Live or dry rock
- Box count
- Displacement
Substrate planning
Reef sand bed calculator
Estimate reef sand, live sand and bag count from tank footprint, depth, coverage, sand type and livestock context.
- Pounds & kilograms
- Bag count
- Depth guidance
Water volume
Reef tank water volume calculator
Estimate actual water volume from tank shape, water height, displacement, sump operating volume, and water change percentage.
- Gallons & liters
- Sand & rock
- Sump volume
Water changes
Reef water change calculator
Estimate water change volume, bucket count, nitrate or phosphate dilution, repeated changes, salinity adjustment and automatic daily schedules.
- Gallons & liters
- Nutrient dilution
- Salinity planning
Saltwater salinity
Reef salinity converter
Convert specific gravity to ppt, ppt to specific gravity, and compare current vs target salinity.
- SG to ppt
- ppt to SG
- Range status
Saltwater mixing
Reef salt mix calculator
Estimate dry reef salt mix from water volume, current salinity, target salinity, and salt mix type.
- Gallons or liters
- ppt or SG
- Water changes
Which reef calculator is right for you?
Choose the situation that best matches the job in front of you. Each tool turns familiar reef tank observations or measurements into a practical planning result.
Plan the reef foundation
Estimate actual water volume first, then plan live rock and sand around the usable footprint and aquascape you want to build.
Use: Reef Tank Water Volume Calculator, Live Rock Calculator, and Reef Sand Bed Calculator.
Prepare and maintain saltwater
Convert salinity readings, calculate a salt mix batch, or plan routine and corrective water changes from your tank's actual water volume.
Use: Reef Salinity Converter, Reef Salt Mix Calculator, and Reef Water Change Calculator.
Understand a coral's care needs
Start with the broader care profile, then check whether the available light and flow are a sensible starting match for that coral.
Use: Coral Care Requirements Lookup, Coral PAR Calculator, and Coral Flow Requirements Finder.
Check compatibility and spacing
Compare care overlap before adding a coral, then assess direct-contact, sweeper, overgrowth, shading, and chemical-interaction risks.
Use: Coral Compatibility Checker and Coral Aggression & Spacing Checker.
Choose a starting placement
Combine light, flow, aggression, and tank zone into a conservative first position. If the coral ID is uncertain, identify it before making major changes.
Use: Coral Placement Finder, Coral Identifier, Coral Guides, and the Coral Database.
How accurate are the tools?
Every result should be treated as planning guidance, not a guarantee. Reef tanks vary by rockwork, lighting spectrum, water clarity, coral history, flow patterns, and maintenance habits. Use the calculators to avoid rushed decisions, then verify important changes with trusted reef references and careful coral observation.
Why use these reef calculators?
2
Beginner-friendly
Short guidance helps you choose the right tool and understand where an estimate has limits.
3
App-ready
Use the result on the web, then continue with photo scans and saved coral history in the app.
Coral Identifier
Identify, compare, and save reef corals.
Calculators help with the setup. The app helps when you are looking at a coral and need a practical photo-based starting point.
